try this in child-theme functions.php:

function custom_replace_burger_anchor_with_button( $items, $args ){ 
    $pattern = '/(<li[^>]*class="[^"]*av-burger-menu-main[^"]*"[^>]*>)\s*<a([^>]*)>/is';
    $items = preg_replace($pattern, '$1<button type="button" $2>', $items);
    $items = preg_replace('/<\/a>(\s*<\/li>\s*$)/', '</button>$1', $items);
    return $items;
}
add_filter( 'wp_nav_menu_items', 'custom_replace_burger_anchor_with_button', 9999, 2 );

BUT: Please note that in this case, you will no longer need to assign all styles to the a tag, but rather to the button tag.
In this case, it might be better to use role=”button” and class=avia-button.

function custom_enhance_burger_anchor_regex( $items, $args ) {
    $pattern = '/<a href="#" aria-label="(.*?)"/i';
    $replacement = '<a href="#" role="button" class="avia-button" aria-label="$1"';  
    $items = preg_replace($pattern, $replacement, $items);
    return $items;
}
add_filter( 'wp_nav_menu_items', 'custom_enhance_burger_anchor_regex', 9999, 2 );

No CSS break: Since it remains an anchor-tag, all Enfold styles for the menu continue to work perfectly.
A11y-compliant: With role=”button,” we tell the screen reader: “Ignore that there is a link here; treat this element like a button.”

maybe it is better to not add the class avia-button because it might come into conflict with some stylings.
use a different class there f.e.: avia-burger-button
then you can easily select it via this class.

try in your child-theme functions.php:

function ava_custom_toggle_behavior(){
?>
<script type="text/javascript">
(function($) {
    $(window).on('load', function() {
        $('.toggler').on('click', function() {
            var $current = $(this);
            
            // Short delay so Enfold can set its own classes
            setTimeout(function() {
                if ($current.hasClass('activeTitle')) {
                    // Find all other togglers on the page that are active
                    $('.toggler').not($current).each(function() {
                        if ($(this).hasClass('activeTitle')) {
                            // Simulate click or remove classes manually
                            $(this).trigger('click');
                        }
                    });
                }
            }, 100);
        });
    });
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'ava_custom_toggle_behavior');

or even better – just use the team-member element as it is and parse a popup by your own.
see with snippet on that example page: https://webers-testseite.de/teammember-vitae-2/
PS: It is always best to examine each individual case closely, as this is the only way to offer a customized solution. Otherwise, one indulges in speculation.

The last solution has the advantage that you only use the pure Enfold element for team members and then create your own lightbox with it. Disadvantage: you would have to rebuild your page and discard our previous design. In the window on the right side of the page, you can see that only plain text is entered in the Description Input Fiele — the Lightbox retrieves the image, name, and position from the existing DOM elements.
To change the aria-label – just edit these lines:

tPrev: 'Previous Biography',
tNext: 'Next Biography',

It depends a little on how you want to use it. If you only want to change this to “next bio” and “previous bio” for certain custom classes, we would need to rewrite this code a little.

f.e. if you have a gallery – then you can give a custom class to that gallery element (f.e. team-member)

function add_magnific_popup_aria_labels() {
    ?>
    <script type="text/javascript">
    (function($) {
        'use strict';
        
        if (typeof $.avia_utilities !== 'undefined' && typeof $.avia_utilities.av_popup !== 'undefined') {
            
            var originalOpenCallback = $.avia_utilities.av_popup.callbacks.open;
            
            $.avia_utilities.av_popup.callbacks.open = function() {
                
                if (typeof originalOpenCallback === 'function') {
                    originalOpenCallback.call(this);
                }
                
                var self = this;
                
                setTimeout(function() {
                    // Determine labels based on the gallery container
                    var prevLabel = 'Previous image';
                    var nextLabel = 'Next image';
                    var closeLabel = 'Close lightbox';
                    
                    // Check if the clicked element (currItem.el) is inside a container with a custom class
                    if (self.currItem && self.currItem.el) {
                        var $link = $(self.currItem.el);
                        
                        // Find the parent lightbox container element
                        var $lightboxContainer = $link.closest('.avia-gallery, .av-masonry, .av-horizontal-gallery');
                        
                        if ($lightboxContainer.hasClass('team-member')) {
                            prevLabel = 'Previous person';
                            nextLabel = 'Next person';
                            closeLabel = 'Close biography';
                        } else if ($lightboxContainer.hasClass('products-gallery')) {
                            prevLabel = 'Previous product';
                            nextLabel = 'Next product';
                            closeLabel = 'Close product gallery';
                        } else if ($lightboxContainer.hasClass('projects-gallery')) {
                            prevLabel = 'Previous project';
                            nextLabel = 'Next project';
                            closeLabel = 'Close project gallery';
                        }
                        // Add more conditions as needed
                    }
                    
                    $('.mfp-arrow-left').attr('aria-label', prevLabel);
                    $('.mfp-arrow-right').attr('aria-label', nextLabel);
                    $('.mfp-close').attr('aria-label', closeLabel);
                }, 50);
            };
            
            var originalChangeCallback = $.avia_utilities.av_popup.callbacks.change;
            
            $.avia_utilities.av_popup.callbacks.change = function() {
                
                if (typeof originalChangeCallback === 'function') {
                    originalChangeCallback.call(this);
                }
                
                var self = this;
                
                // Update labels when changing images
                var prevLabel = 'Previous image';
                var nextLabel = 'Next image';
                
                if (self.currItem && self.currItem.el) {
                    var $link = $(self.currItem.el);
                    var $lightboxContainer = $link.closest('.avia-gallery, .av-masonry, .isotope, .av-horizontal-gallery');
                    
                    if ($lightboxContainer.hasClass('team-member')) {
                        prevLabel = 'Previous person';
                        nextLabel = 'Next person';
                    } else if ($lightboxContainer.hasClass('products-gallery')) {
                        prevLabel = 'Previous product';
                        nextLabel = 'Next product';
                    } else if ($lightboxContainer.hasClass('projects-gallery')) {
                        prevLabel = 'Previous project';
                        nextLabel = 'Next project';
                    }
                }
                
                $('.mfp-arrow-left').attr('aria-label', prevLabel);
                $('.mfp-arrow-right').attr('aria-label', nextLabel);
            };
        }
        
    })(jQuery);
    </script>
    <?php
}
add_action('wp_footer', 'add_magnific_popup_aria_labels', 999);

you see this line includes masonry etc. if you like:

// Find the parent lightbox container element
var $lightboxContainer = $link.closest('.avia-gallery, .av-masonry, .av-horizontal-gallery');

Solutions
This security issue has a low severity impact and is unlikely to be exploited.

maybe it is not so urgent ;)

____________________
Perhaps it’s time to introduce a nonce solution for all Enfold scripts?
(for my own i have written a small plugin that will bring to every script/inline-script a nonce-key; and my csp directive says:
script-src ‘nonce-key==’ ‘strict-dynamic’ ) that is the best against XSS – and check f.e. on: https://securityheaders.com/?q=https%3A%2F%2Fwebers-testseite.de&followRedirects=on )

PS – if you only want to avoid that on small screens the slider images will be less height then the inner content. there will be an option to have a min-height for it:

Which content in the code block does this refer to? That animated typwriting heading?

In addition to the important settings mentioned above by Ismael (spf-record, DKIM1 and DMARC), you should definitely follow the recommendation to send via SMTP.

If you wish to send the form using an email address that does not belong to the domain, it is advisable to include this domain in your SPF record for the domain from which it is being sent.

by the way –

was meinst du mit “mit Dreamweaver eingesetzt” ?
(ich kenne Adobe Dreamweaver – aber warum mit dem hier arbeiten? poedit speichert doch die Files ab?)

die po files sind übrigens nicht die, die herangezogen werden – sondern die mo-files die po sind zum editieren gedacht. ;)

kannst du deine child-theme functions.php mal posten?

sometimes the way via youtube api v3 does not work – even if you have connected your billing details with that api.

place a snippet to your child-theme funcions.php:
– Registering the shortcode for the descriptive text (without api use – and google costs ;)

/**
 * Final Version: Fetches YouTube description and converts links correctly
 * preventing double-tagging or broken HTML.
 */
function get_yt_description_final($atts) {
    $a = shortcode_atts(array('id' => ''), $atts);
    if (empty($a['id'])) return 'Video ID missing.';

    $v_id = esc_attr($a['id']);
    
    // Use a fresh cache key to overwrite the broken HTML in your database
    $transient_key = 'yt_desc_v3_clean_' . $v_id;
    $description = get_transient($transient_key);

    if (false === $description) {
        $response = wp_remote_get("https://www.youtube.com/watch?v=" . $v_id, array(
            'user-agent' => 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/115.0.0.0 Safari/537.36'
        ));

        if (is_wp_error($response)) return 'YouTube connection error.';

        $html = wp_remote_retrieve_body($response);

        if (preg_match('/"shortDescription":"(.+?)"/', $html, $matches)) {
            $description = $matches[1];
            
            // Decode unicode characters
            $description = json_decode('"' . $description . '"');
            
            // Clean up backslashes before storing
            $description = stripslashes($description);
            
            set_transient($transient_key, $description, DAY_IN_SECONDS);
        } else {
            return 'Description currently unavailable.';
        }
    }

    // 1. First: Escape the raw text to be safe from XSS
    $safe_desc = esc_html($description);

    // 2. Second: Convert URLs into clickable links using a more precise regex
    // This regex matches URLs starting with http or https
    $pattern = '~(?<!["\'>])\bhttps?://[^\s()<>]+(?:\([\w\d]+\)|([^[:punct:]\s]|/))~';
    $clickable_desc = preg_replace($pattern, '<a href="$0" target="_blank" rel="nofollow">$0</a>', $safe_desc);

    // 3. Output the result
    return '<div class="yt-desc-box" style="white-space: pre-wrap; word-break: break-word; background:#f9f9f9; padding:20px; border-radius:5px; border:1px solid #ddd; height:350px; overflow-y:auto;">' 
           . $clickable_desc . 
           '</div>';
}
add_shortcode('video_description', 'get_yt_description_final');

after that – place a shortcode under your embedded video:
[video_description id="youtube-ID"]

see: https://webers-testseite.de/videos/
( there you can easily copy&paste the needed code – and see examples )

because i do not believe that this is GDPR konform – i block it til you accept to see the youtube video.

du kannst ein child-theme language file hochladen (musst allerdings beide files hochladen po und mo file).
Je nachdem welches lang file du nutzt – ich gehe mal von Du (nicht förmlich) aus. Dann musst du das file de_DE.po bearbeiten.
Das geht ganz gut mit poedit: https://poedit.net/download
Damit öffnest Du das file und kannst nach dem String “Suchergebnis nicht zufriedenstellend” suchen. Es gibt wohl nur eine Fundstelle. Das ersetzt du und speicherst dann ab. poedit generiert automatisch die dazugehörige mo datei.
Beide files lädst du in dein child-theme/lang folder hoch ( der existiert nicht – erstelle ihn) –
danach setzt du in die child-theme functions.php folgendes ein:

function overwrite_language_file_child_theme() {
    $lang = get_stylesheet_directory().'/lang';
    return $lang;
}
add_filter('ava_theme_textdomain_path', 'overwrite_language_file_child_theme');

von da an wird nun das file für die Übersetzungen genommen.

________________________

PS: wenn es nur um diese eine Übersetzung geht (oder ein paar mehr) dann kannst du die Phrase auch so überschreiben – ohne ein child-theme lang file zu haben:

function my_text_strings( $translated_text, $text, $domain ){
  switch ( $translated_text ){
    case 'Suchergebnis nicht zufriedenstellend? Versuche es mal mit einem Wort oder einer anderen Schreibweise'  :  $translated_text = __( 'neue Phrase', $domain ); 
    break;
    case 'eine andere Ersetzung'  :  $translated_text = __( 'neue Phrase Nr. 2', $domain ); 
    break;
  }
  return $translated_text;
}
add_filter('gettext', 'my_text_strings', 20, 3);

bei solch langen Phrasen – geht das, da man nicht Gefahr läuft das die zufällig woanders noch auftauchen – schwierig wird es bei kurzen Begriffen.

12 years ago ? this seems to be deprecated.
anyway: on the images of your slider – you have set on: advanced tab – link options – lightbox ?

here is a way to have the option by classes to style those sticky posts by an own selector:

/**
 * Add a custom CSS class to sticky posts for styling purposes
 */
function add_sticky_classes( $classes, $class, $post_id ) {
    if ( is_sticky($post_id) ) {
        $classes[] = 'is-sticky-post';
        $classes[] = 'stickypost-' . $post_id;
    }
    return $classes;
}
add_filter( 'post_class', 'add_sticky_classes', 10, 3 );

/* Style sticky items in Masonry */
.is-sticky-post .av-inner-masonry::after {
    content: 'Featured';
    position: absolute;
    top: 10px;
    right: 10px;
    background: #000;
    color: #fff;
    padding: 2px 8px;
    font-size: 10px;
    text-transform: uppercase;
    z-index: 5
}

can you test this instead ( and remove your solution temporarly ) :

/**
 * Enfold Masonry Filter: Show sticky posts first, followed by other entries (including CPTs)
 * This filter captures selected post types dynamically from the element settings.
 */
function avia_masonry_entries_query_mod($query, $params) {
    // Prevent the filter from running in the WordPress admin backend
    if (is_admin()) {
        return $query;
    }

    // 1. Get the IDs of all sticky posts
    $sticky = get_option('sticky_posts');
    
    // If no sticky posts exist, return the original query without modifications
    if (empty($sticky)) {
        return $query;
    }

    // 2. Fetch IDs for the remaining posts (including Custom Post Types)
    // We use $params['post_type'] to dynamically support whatever is selected in the Masonry element
    $args = array(
        'post_type'      => $params['post_type'], 
        'post__not_in'   => $sticky,         // Exclude stickies so they aren't duplicated
        'posts_per_page' => -1,              // Fetch all IDs to ensure we have enough for the merge
        'fields'         => 'ids',           // Performance optimization: only fetch IDs
    );

    // If a specific taxonomy/category is selected in the element, apply it to our helper query
    if (!empty($params['taxonomy'])) {
        $args['tax_query'] = array(
            array(
                'taxonomy' => $params['taxonomy'],
                'field'    => 'id',
                'terms'    => explode(',', $params['categories']),
            ),
        );
    }

    $other_posts = get_posts($args);

    // 3. Merge the arrays: Stickies first, then the remaining posts
    $combined_ids = array_merge($sticky, $other_posts);

    // 4. Sanitize the IDs (ensure they are integers)
    $query['post__in'] = wp_parse_id_list($combined_ids);
    
    // 5. Force the Masonry to respect the exact order of our merged array
    $query['orderby'] = 'post__in'; 
    $query['order']   = 'ASC'; 
    
    // Set the final limit of items to display
    $query['posts_per_page'] = 6; 

    // Disable default sticky handling to prevent WP from interfering with our custom order
    $query['ignore_sticky_posts'] = true;

    return $query;
}
add_filter('avia_masonry_entries_query', 'avia_masonry_entries_query_mod', 10, 2);

you can use f.e. keka (download) to compress or : you can still download a little app i wrote. it is a shell-script. Just unzip that file and place the app to your desktop.
Now you can drag&drop files or folders to that icon. If you do not enter a new name – the generated zip will be named as the source file or folder:

https://webers-testseite.de/zip-it.zip
because it is then an app from the internet you had to allow it on OSX the first time to execute.

(sorry these are screenshots from my german OSX Mac.)
do not move to bin – klick the gray button and then open : system preferences – Data protection and security and on Security allow the app to open anyway.

see here how i made that automator app: https://kriesi.at/support/topic/how-to-submit-and-use-custom-fonts/#post-1470903

the downloaded app will have now an included icon and it will look like this :

see here for keka usage: https://kriesi.at/support/topic/trouble-importing-tff-or-woff-fonts/#post-1492002

_____________ :lol
PS: That’s only because I’m lazy. For example, I also created an Automator app that converts an mkv with dts sound into an mkv with ac3 sound via ffmpeg. Without remuxing the video ;)