try first this shorter form – maybe that will work for you.
(do not know if the old filter is still ther avia_ …)
there are more complex snippets – but in almost all installations this will work:

function enfold_customization_postnav($settings){
  $settings['skip_output'] = false;
  $settings['same_category'] = true;
  return $settings;
}
add_filter('avf_post_nav_settings','enfold_customization_postnav', 10, 1);

edit: here is one with more options:

function my_avf_post_nav_settings( array $settings ){
  if( true === $settings['is_hierarchical'] ){
    $settings['skip_output'] = true;
    return $settings;
  } 
  if( ! in_array( $settings['type'], array( 'post', 'portfolio' ) ) ){
    $settings['skip_output'] = true;
    return $settings;
  }
  $settings['same_category'] = true;
  $settings['is_fullwidth'] = false;
  $settings['skip_output'] = false; 
  return $settings;
}
add_filter( 'avf_post_nav_settings', 'my_avf_post_nav_settings', 10, 1 );

Are you talking about the tooltips displayed by the browser itself when hovering over the image?
They appear automatically if the image has a title attribute.

However, if you have a gallery that displays images in a lightbox, this title attribute is also displayed as text in the bottom bar of the lightbox. Completely removing the title tag would therefore be suboptimal. For galleries, you can switch to displaying the description or caption instead, but this is not possible for all Enfold elements.
So if it only affects the galleries on your site, you could do that, but you would then have to update the description of the images, for example.

There is a snippet that, when placed in the child theme’s functions.php, temporarily removes this title tag on hover but adds it back when clicked:

function temporary_removal_title_tags(){
?>
<script>
  window.onload = function() {
    var elementsWithTitle = document.querySelectorAll('a, img, *[title]');
    for (var i = 0; i < elementsWithTitle.length; i++) {
        var element = elementsWithTitle[i];

        element.setAttribute("data-original-title", element.title);

        element.addEventListener("mouseenter", function() {
            this.title = ""; 
        });

        element.addEventListener("mouseleave", function() {
            this.title = this.getAttribute("data-original-title"); 
        });

        element.addEventListener("mousedown", function() {
            this.title = this.getAttribute("data-original-title");
        });
    }
  };
</script>
<?php
}
add_action('wp_footer', 'temporary_removal_title_tags');

here you see that this script is working for all anchor elements or images – or all elements that have a title-tag

maybe that option for logo and Navigation on Enfold – Header : “Let Logo And Menu Position Adapt To Browser Window” is a possibility.
Because your navigation is overlapping your logo on smaller screens.

on your landing page (no enfold page ) or on the other pages?
(ok www leads to a different landing page )

First hint – your logo got quite a lot of white space around the green logo inside.
So unless the corporate design specifies that there should be so much white space around the actual logo, I would change that first.

css depends on the place where you show it – f.e. in the top header:

#top #wrap_all .av-social-link-bluesky:hover a {
    color: #fff;
    background-color: #1185fe;
}
#top #wrap_all .av-social-link-bluesky a svg * {
    fill: var(--enfold-header_replacement_menu_color);
}
#top #wrap_all .av-social-link-bluesky a:hover svg * {
    fill: #FFF
}

now – thanks for the admin permissions.

i did what i mentioned above: for the thumbs in grid i take the portfolio size (495×400)
using that snippet to have original images in the ajax preview image ( on imagify you have choosen to have no compression – so original image might be of less file-size than the recalculated large image-size )
and disabeling the enfold option to use lazyloading ( maybe the option of wp-rocket is better )

but with these changings – you can see a much better loading performance.

in additon – i decided to show on lightbox the full image ( because your large recalculated images are much bigger in file-size than the full one )
and to have no scroll on background – on opend lightbox.

you know that and how you can add your own social media icons to the enfold system.

can we influence the image shown in the ajax preview ( that img insided avia-gallery-big ) – it seems to use the recalculated “large” image.
But as you know this might be bigger in file size than the original uploaded image!
I can not find a filter to adjust it.

or could we influence it by
$params['preview_size'] = apply_filters( 'avf_ajax_preview_image_size', 'gallery' );

i can find this in portfolio.php

//	create array with responsive info for lightbox
	$img = Av_Responsive_Images()->responsive_image_src( $attachment->ID, 'large' );

bring it to full will often reduce file-size – as you know that Enfold standard compression leads to bigger file-sizes on large image.

ok – i found the place to change in gallery.php (line 757)
$prev = wp_get_attachment_image_src( $attachment->ID, $preview_size );

if we would use :
$prev = wp_get_attachment_image_src( $attachment->ID, 'full' );

looking to his page f.e.:
the krebs-treppen-systeme-gelaender-system30-3.jpg is 121kb
but krebs-treppen-systeme-gelaender-system30-3-1030×839.jpg is 268kb

the whole page got over 112MB images – and could be reduced to a half size.

you can find the defintions of standard icons on enfold/includes/config-enfold/init-base-data.php

Easy Slider is on default using:

'svg__next_big'  	=> array( 'font' => 'svg_entypo-fontello', 'icon' => 'right-open-big' ),
'svg__prev_big'  	=> array( 'font' => 'svg_entypo-fontello', 'icon' => 'left-open-big' ),

The Filter you can use to change these icons is: avf_default_icons

you can use it like this in your child-theme functions.php:

function avia_replace_default_icons($icons){
// e.g.: changed by uploaded svg files - using the ID's and the font-name is svg_wp-media-library
	$icons['svg__prev_big'] =  array( 'font' =>'svg_wp-media-library', 'icon' => '50913');
	$icons['svg__next_big'] =  array( 'font' =>'svg_wp-media-library', 'icon' => '50591');     
	return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

but: What is the font-name of your uploaded icon-set

you find that information on :

now f.e. if you like to replace these standard icons by icons of the iconset : medical

function avia_replace_default_icons($icons){
	$icons['svg__prev_big'] =  array( 'font' =>'medical', 'icon' => 'uf101');
	$icons['svg__next_big'] =  array( 'font' =>'medical', 'icon' => 'uf135');     
	return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

you can find those font icon codes f.e. on trying to place that icon you like to have and hover it :
( it is the value inside the brackets – without that backslash)