hm i did not try that because in class-avia-slideshow.php this parameter is missing on the array:

$video_data = apply_filters( 'avf_youtube_video_data', array(
	'autoplay' 		=> 0,
	'videoid'		=> $video_id,
	'hd'			=> 1,
	'rel'			=> 0,
	'wmode'			=> 'opaque',
	'loop'			=> 0,
	'version'		=> 3,
	'autohide'		=> 1,
	'color'			=> 'white',
	'controls'		=> $controls,
	'iv_load_policy'=> 3
));

but: as always, it only works muted.
Thanks Ismael – i will keep that snippet in mind. btw: then you can set an end time too:

add_filter( 'avf_youtube_video_data', function( $data ) {
    if( !empty( $data['videoid'] ) && $data['videoid'] === 'G0k3kHtyoqc' ) {
        $data['start'] = 15;
	$data['end'] = 40;
    }
    return $data;
});

However, the video behaves this way only when first called up. Once the slideshow has run through its first cycle, these settings are no longer taken into account. Furthermore, if you have selected autoplay, the video will be interrupted after the slider autorotation duration and the next slide will be called up.

if you like to have the pipes between the links:
adjust the new switch point when the links goto a twoliner:

@media only screen and (max-width: 467px) {
  #header {
    height: 160px !important;
    max-height: 160px !important;
  }
  .responsive.html_header_top.html_mobile_menu_tablet  #top #main {
    padding-top: 160px !important;
  }
} 

and for phone-info:

/******  styling the phone-info links with pipe separator  *************/
#top #header_meta .phone-info {
  display: flex;
  flex-flow: row wrap;
  gap: 0 40px; 
}

#top #header_meta .phone-info a {
  flex:  1 1 auto;
  position: relative;
}

#top #header_meta .phone-info a:not(:last-child)::after {
  content: '|';
  font-size: 18px;
  position: absolute;
  right: -24px; 
  color: #FFF;
}

There is a lot more to think of.
First – to style the header_meta with your phone-info entries.
To prevent breaks occurring where it looks unsightly, it would be a good idea to replace your entries completely with this line:

<a style="white-space: nowrap" href="/over-ons/">Over Ons</a><a style="white-space: nowrap" href="/veelgestelde-vragen/">Veel gestelde vragen</a><a style="white-space: nowrap" href="#">Nieuws</a><a style="white-space: nowrap" href="tel:+31434551268">T: +31 (0)43 455 12 68</a>

after that we will see if the pipes are neccessary.

On mobile devices, these links become two lines—and this must also be taken into account with the padding-top of main.

After you have these new phone-info – remove your code from above and try:

@media only screen and (max-width: 989px) {
  .responsive #top #wrap_all #header .container {
    width: 95%;
    max-width: 95%;
  }

  #header {
    position: fixed !important;
    height: 110px !important;
    max-height: 110px !important;
  }

  .responsive.html_header_top.html_mobile_menu_tablet  #top #main {
    padding-top: 110px !important;
  }

  #top #header.av_header_transparency #header_meta {
    background-color: transparent;
  }

  #header_main {
    border-bottom: none;
  }

  #header:not(.av_header_transparency) #header_main {
    box-shadow: 0 5px 10px #eee;
  }

  .responsive #top .av-logo-container ,
  .responsive #top .logo a,
  .responsive #top .logo img,
  .responsive #top .logo svg {
    height: 80px !important;
    max-height: 80px !important;
    line-height: 80px !important;
  }

  .responsive #top #avia-menu > .menu-item-avia-special > a {
    height: 80px !important;  ;
    line-height: 80px !important; 
  }

  .responsive.html_mobile_menu_tablet #top #wrap_all .av_header_transparency {
    background-color: transparent !important;
  }

  .responsive #top .header_bg {
    opacity: 1;
    filter: alpha(opacity=100);
    background-color: #FFF !important;
  }  

  #top #header:not(.av_header_transparency) .header_bg {
    background-color: #FFF !important;
  }

  .responsive.html_mobile_menu_tablet #top .av_header_transparency .logo img.alternate, 
  .responsive.html_mobile_menu_tablet #top .av_header_transparency .logo .subtext.avia-svg-logo-sub {
    display: block !important;
  }

  .responsive.html_mobile_menu_tablet #top .av_header_transparency.av_alternate_logo_active .logo a > img, 
  .responsive.html_mobile_menu_tablet #top .av_header_transparency.av_alternate_logo_active .logo a > svg {
    opacity: 0;
  }

  .html_mobile_menu_tablet .header_color  #header.av_header_transparency div .av-hamburger-inner, 
  .html_mobile_menu_tablet .header_color  #header.av_header_transparency div .av-hamburger-inner::before, 
  .html_mobile_menu_tablet .header_color  #header.av_header_transparency div .av-hamburger-inner::after {
    background-color: #FFF;
  }
  .html_mobile_menu_tablet .header_color  #header.av_header_transparency .menu-item-search a:before {
    color: #FFF;
  }
}

@media only screen and (max-width: 767px) {
  #header {
    position: fixed !important;
    height: 140px !important;
    max-height: 140px !important;
  }

  .responsive.html_header_top.html_mobile_menu_tablet #top #main {
    padding-top: 140px !important;
  }
}

@media only screen and (max-width: 435px) {
  #header {
    position: fixed !important;
    height: 160px !important;
    max-height: 160px !important;
  }
  .responsive.html_header_top.html_mobile_menu_tablet  #top #main {
    padding-top: 160px !important;
  }
} 
/****** End *************/

/******  styling the phone-info links  *************/
#top #header_meta .phone-info {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-evenly;
  gap: 0 30px;
}

Then I sincerely hope that translation errors like those in “The Hungarian Phrasebook” don’t creep in.
https://youtu.be/grA5XmBRC6g?si=Mqnuk1FpjPJAipeQ&t=50

Please leave technical terms untouched, as they are commonly used.
A button is simply a button, and you can hover it, etc. …

If you absolutely want such translations, get the corresponding Lang file from the Lang folder (only po is needed to edit).
Open the po-file in f.e. poedit (free po editor) Search for your Phrase – f.e. “Show Fullscreen Button (HTML5 videos)”
Enter your translation and save (poedit will save the new po-file and generates the concerning mo-file too).
Upload these files to your child-theme/lang/ folder and put this to your child-theme functions.php:

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

keep the sequence of variables inside your translation.
F.e. : But we are proud to say that %s contributed %s entries already.
first the name of the author for %s – then the number of contributions for %s

e.g. for german translations:
Wir sind jedoch erfreut, dass %s bereits %s Beiträge beigesteuert hat.
and not:
Wir sind jedoch erfreut, dass bereits %s Beiträge von %s beigesteuert wurden.

i do not see where your code misses some settings:
f.e. where does this comes from?

#top .av_inherit_color * {
  color: inherit;
}

try in your quick css:

#top .av-large-testimonial-slider .avia-testimonial_inner {
    display: inline-table;
}

#top .av-large-testimonial-slider .avia-testimonial_inner * {
  color: #FFF;
}

#top .avia-slider-testimonials.av-slideshow-ui .avia-slideshow-arrows a {
  color: #FFF;
  opacity: 1 !important;
}

#top .alternate_color .avia-slider-testimonials.av-slideshow-ui .avia-slideshow-arrows a.avia-svg-icon svg:first-child {
  fill: #FFF !important;
  opacity: 0.5;
}

#top .alternate_color .avia-slider-testimonials.av-slideshow-ui .avia-slideshow-arrows a.avia-svg-icon:hover svg:first-child {
  opacity: 1
}

Give your visitors a bit more time to read the testimonial – ( autorotation is to fast )

__________
btw:
you entered the custom class with a dot on Link
Enter it without
nevertheless it is added correctly to avia-testimonial-wrapper

there are some Plugins that will offer such a function: CatalogX (Freemium) or WooCommerce Catalog Mode
or you might use code snippets – but it is not as easy as it sounds. There are still backdoors that can be used to find something.

but this might give you a chance to exclude some Products by slugs ( f.e.: members-only or premium)

This is what an AI like Claude would give to you:

// 1. Hide from queries
add_action('pre_get_posts', 'hide_member_products_from_guests');
function hide_member_products_from_guests($query) {
    if (is_admin() || !$query->is_main_query()) {
        return;
    }
    
    if (!is_user_logged_in()) {
        $tax_query = $query->get('tax_query') ?: array();
        
        $tax_query[] = array(
            'taxonomy' => 'product_tag',  // product_cat → product_tag
            'field'    => 'slug',
            'terms'    => array('members-only', 'premium'),  // Deine Tag-Slugs
            'operator' => 'NOT IN'
        );
        
        $query->set('tax_query', $tax_query);
    }
}

// 2. Visibility Filter
add_filter('woocommerce_product_is_visible', 'filter_member_products_visibility', 10, 2);
function filter_member_products_visibility($visible, $product_id) {
    if (!is_user_logged_in()) {
        if (has_term('members-only', 'product_tag', $product_id)) {  // product_cat → product_tag
            return false;
        }
    }
    return $visible;
}

// 3. Block direct access
add_action('template_redirect', 'block_member_product_access');
function block_member_product_access() {
    if (!is_user_logged_in() && is_product()) {
        global $post;
        if (has_term('members-only', 'product_tag', $post->ID)) {  // product_cat → product_tag
            wp_redirect(wp_login_url(get_permalink()));
            exit;
        }
    }
}

// 4. Exclude from search (maybe an ajax pendent is needed too)
add_filter('posts_where', 'exclude_member_products_from_search', 10, 2);
function exclude_member_products_from_search($where, $query) {
    global $wpdb;
    
    if (!is_admin() && $query->is_search() && !is_user_logged_in()) {
        $where .= " AND {$wpdb->posts}.ID NOT IN (
            SELECT object_id FROM {$wpdb->term_relationships}
            INNER JOIN {$wpdb->term_taxonomy} ON {$wpdb->term_relationships}.term_taxonomy_id = {$wpdb->term_taxonomy}.term_taxonomy_id
            INNER JOIN {$wpdb->terms} ON {$wpdb->term_taxonomy}.term_id = {$wpdb->terms}.term_id
            WHERE {$wpdb->terms}.slug IN ('members-only', 'premium')  // Deine Tags hier
            AND {$wpdb->term_taxonomy}.taxonomy = 'product_tag'  // product_cat → product_tag
        )";
    }
    
    return $where;
}

// 5. Exclude from REST API 
add_filter('woocommerce_rest_prepare_product_object', 'hide_member_products_from_api', 10, 3);
function hide_member_products_from_api($response, $object, $request) {
    if (!is_user_logged_in() && has_term('members-only', 'product_tag', $object->get_id())) {  // product_cat → product_tag
        return new WP_Error('rest_forbidden', 'Zugriff verweigert', array('status' => 403));
    }
    return $response;
}

just for understanding – these are the default values from loop-author.php:

// Default arguments for Author Loop
$default_args = array(
    'type'              => 'grid',
    'columns'           => 4,
    'items'             => get_option('posts_per_page', 12), // WordPress setting, fallback: 12
    'contents'          => 'excerpt_read_more',
    'preview_mode'      => 'auto',
    'image_size'        => 'portfolio',
    'paginate'          => 'no',
    'class'             => '',
    'show_modified_date' => 'no',  // 'yes' or 'no' - shows "Updated: XX" if post was modified
    'orderby'           => 'date',  // 'date', 'modified', 'title', 'rand', 'comment_count', 'menu_order'
    'order'             => 'DESC',  // 'DESC' (newest first) or 'ASC' (oldest first)
    'fallback_image'    => 'placeholder',      //  'placeholder'  or URL to fallback image 
    'post_types'        => array('post'), // Array: array('post'), array('portfolio'), or array('post', 'portfolio')
);

// Content Options for 'contents' parameter:
    // 'title'                  - Title only
    // 'title_read_more'        - Title and Read More button
    // 'only_excerpt'           - Excerpt only (no title)
    // 'only_excerpt_read_more' - Excerpt and Read More button (no title)
    // 'excerpt'                - Title and Excerpt
    // 'excerpt_read_more'      - Title, Excerpt and Read More button (default)

if you like to have it this way (grid, 4columns, exerpt with readmore, only posts ordered by date – newest first) you do not need to set the filter.
Then only the second part is needed inside functions.php.

The filter could do more – you can even differ between authors – f.e by author name. :

// 1. Layout for different authors by ID
add_filter( 'avf_author_loop_args', function( $atts, $context ) {
    if( $context == 'author' ) {
        // Common settings for all author pages
        $atts['items']             = -1;
        $atts['image_size']        = 'gallery';
        $atts['contents']          = 'excerpt_read_more';
        $atts['post_types']         = array('post', 'portfolio'); 
		
	// Fallback-Image from Media Library (Attachment-ID)
        $fallback_id = 2052;  // Your image ID from Media Library
        $fallback_img = wp_get_attachment_image_src($fallback_id, $atts['image_size']);
        $atts['fallback_image'] = $fallback_img ? $fallback_img[0] : 'placeholder';
        
        $author_slug = get_query_var( 'author_name' );

        // Individual configuration for a specific author
        if( $author_slug == 'guenni007' ) {
            $atts['type']              = 'grid';
            $atts['columns']           = 3;
        } 
        else {
            // default setting for the rest
            $atts['type']              = 'list';
        }
    }
    return $atts;
}, 10, 2);

the fallback image i get from media-library with the attachment ID
Advantage of this solution – the fallback image is based on the selected image size setting.

see:
grid for guenni007: https://basis.webers-testseite.de/author/guenni007/
list for johndoe: https://basis.webers-testseite.de/author/johndoe/

So far, it only displays posts – now I’m trying to implement a way to select the post type via $atts['post_types'] – so the author page could show all posts and portfolios from an author.
btw. Something that handles the standard file ‘loop-author.php’ in exactly the same way: it only displays the posts.
Will I manage to fix that too?

Edit : see solution on: https://kriesi.at/support/topic/how-to-customize-the-author-page/#post-1491667

just a moment – pastebin code is edited now _ the read-more button is buggy. …
…. it is fixed now – download from above

… maybe we should take out the readmore button – and place it as a sibling to av-author-grid-content. So we can then position it to always be on the bottom of equal height articles. … more to come

i try now to have a pagination by atts settings.

All my installations run without jQuery Migrate — all plugins and themes are up to date — I don’t think jQuery Migrate is needed.
You can test it

by the way: if you are on instagram page – they have as favicon a png file:

next : if you have the burger icon on the left – maybe you prefer to have that slide-out too from the left:

.av-burger-overlay-scroll {
  width: 250px;
  left: -250px;
  max-width: 100%;
  transition: all 0.5s cubic-bezier(0.75,0,0.25,1);
}

.html_av-overlay-side .av-burger-overlay-scroll {
  left: 0;
  max-width: 100%;
  transform: translateX(-250px);
  transition: all 0.5s cubic-bezier(0.75,0,0.25,1);
}

Sorry, no private content for me—I’m just a participant as you are. So you’ll have to wait until the mods respond to you.

btw. maybe your filter add_avia_builder_post_type_option had to be activated first.

add_theme_support('add_avia_builder_post_type_option' );