Yes – there is a definition for those quotes in enfold-functions.php with avia_ampersand function.
but even if i overwrite that function ( as a pluggable function – it is easy to do ) i can not set for quillemets ( » and. « )

i think that the lang setting for that page is disturbing the way it might work.
…

if you are using the de_X setting for your page try this in your child-theme functions.php:

for copy and paste the function ( do not copy the leading <?php see pastbin : https://pastebin.com/JQfUCDqZ

PPS: all credits goes to : https://www.buchundberger.net/blog/stefan-buchberger/

hm – tested it on newest Enfold – seems not to work as expected – and even the known snippet of generating groups – does not work anymore in that manner that even if there are images in text-block element with that group-class are together in one Group.
Between Image Alb even in different color-sections the snippet works!

(on using group-1, group-2 etc. )

function handle_lightbox_groups_in_gallery(){
?>
<script>
(function($){
    $(window).on('load',function() {
        $('.group-1 .lightbox-added').attr('data-group', '1');
        $('.group-2 .lightbox-added').attr('data-group', '2');
        $('.group-3 .lightbox-added').attr('data-group', '3');
        $('.group-4 .lightbox-added').attr('data-group', '4');
        $('.group-5 .lightbox-added').attr('data-group', '5');
        $('.group-6 .lightbox-added').attr('data-group', '6');
        $('.group-7 .lightbox-added').attr('data-group', '7');
        $('.group-8 .lightbox-added').attr('data-group', '8');
        // …

        var groups = {};
        $('.lightbox-added').each(function() {
          var id = parseInt($(this).attr('data-group'), 10);
          if(!groups[id]) {
            groups[id] = [];
          }
          groups[id].push( this );
        });

        $.each(groups, function() {
          $(this).magnificPopup({
              type: 'image',
              mainClass: 'avia-popup mfp-zoom-in mfp-image-loaded',
              closeOnContentClick: false,
              closeBtnInside: false,
              gallery: { enabled:true }
          })
        });
    });
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'handle_lightbox_groups_in_gallery');

You do not need to make absolute settings for the scope of the slide out. Relative settings are also accepted here:
In the meantime, the distribution of the property: backdrop-filter is very good, so that it is now quite possible to use it with high browser support.
It will offer you a kind of frosted glas effect for the slide-out.

@media only screen and (min-width:990px){
  .av-burger-overlay-scroll {
    background-color: rgba(255,255,255,0.7) !important;
    width: 40% !important;
    -webkit-backdrop-filter: blur(8px);
    backdrop-filter: blur(8px);
  }
}

So you don’t have to set this class for all home pages, just leave the lines included.
For the other grid-row elements you then have to set the custom-class gridrow-special

function get_rid_of_flex_cell_inner(){ 
?>
<script type="text/javascript">
window.addEventListener("DOMContentLoaded", function () { 
  (function($) {
    $('#top.home #av-layout-grid-1 .flex_cell_inner > *').unwrap();
    $('#top .gridrow-special .flex_cell_inner > *').unwrap();
  })(jQuery);
});
</script>
<?php
}
add_action('wp_footer', 'get_rid_of_flex_cell_inner');

@media only screen and (min-width: 768px) {
  .responsive #top.home #wrap_all #av-layout-grid-1 .flex_cell,
  .responsive #top #wrap_all #main .gridrow-special .flex_cell {
    padding-bottom: 100px !important
  }
  #top.home #av-layout-grid-1 .avia-button-wrap,
  #top #wrap_all #main .gridrow-special .avia-button-wrap {
    position: absolute;
    top: calc(100% - 80px);
    width: 33%;
  }
}

It goes without saying that if you take 4 grid cells you have to adjust the width of the button-wrapper to 25%.
If you switch at 989px – you need to change the media query to that as well.

the problem with it is the flex_cell_inner container – it hampers the absolute positioning of the button-wrapper.

if you need this more than once – give a custom-class to those grid-rows – i now adjusted the code to that page only by ID.
so to get rid of that container under preserving the child elements put this to your child-theme functions.php

function get_rid_of_flex_cell_inner(){ 
?>
<script type="text/javascript">
window.addEventListener("DOMContentLoaded", function () { 
  (function($) {
    $('#top.home #av-layout-grid-1 .flex_cell_inner > *').unwrap();
  })(jQuery);
});
</script>
<?php
}
add_action('wp_footer', 'get_rid_of_flex_cell_inner');

put this to your quick css:

@media only screen and (min-width: 768px) {
  .responsive #top.home #wrap_all #av-layout-grid-1 .flex_cell {
    padding-bottom: 100px !important
  }
  #top.home #av-layout-grid-1 .avia-button-wrap {
    position: absolute;
    top: calc(100% - 80px);
    width: 33%;
  }
}

EDIT: – sorry i see that you got a lot of translations – so best ist to give a custom-class to that grid-row ( on all translated pages )
e.g. : gridrow-special and use that

If it is only that page – it is on all translations the home page – so #top.home will be a good selector for it – see above

Yes mike – but this is half the solution it could be.
Better would be :

maybe it is possible for a mod to change the code for a more global use, in the sense that only pages without transparent logo will have this filter.

do you need inline svg for that alternative logo – or is a img src ok?
see: https://webers-web.info/impressum/

the trick will be to insert another subtext logo. But this logo is not in dependency to av_header_transparency but to header-scrolled class.

Edit: just a moment – i had to optimize the codes

https://vimeo.com/832590165

And you used that option on editing the images slides ( click on those images ) on that second popup window to get the overlay:

Doing this on the slides itself is nice to change the overlay color for each image/video

you want only an image – or a slideshow as body background?
A fullscreen image is easy to have ( if you have on general Layout a boxed or fixed frame layout) – on enfold options: general styling : “body background”
You have all those options to insert even a seamless background-image and have background-repeat etc.
It is then simply implemented by means of a newly created extra container: bg_container.

.bg_container {
  background-image: url(/wp-content/uploads/…);
  background-position: center center;
  background-attachment: fixed;
  background-repeat: no-repeat;
  background-size: cover;
  height: 100%;
  width: 100%;
  position: fixed;
  z-index: -1;
  top: 0;
  left: 0;
}

this is the fixed version – but you can have different options.
see on css-tricks: https://css-tricks.com/perfect-full-page-background-image/

The problem on that is that enfold organizes the entries (artikles) on a grid layout by column setting.
See here example page of enfold grid layout blog: https://kriesi.at/themes/enfold-2017/blog/blog-default/
if you take a look on developer tools you see that on a 3column grid groups of 3 entries are build to have that layout:
in a three-column grid layout, 3 entries each have their own wrapper

(click to enlarge the image)

so if you have the chance to handle the whole grid as one wrapper and have some media queries to style them you had to bring all entries to one wrapper
put this to your child-theme functions.php

function wrap_articles_in_one_flex_container(){ 
?>
<script type="text/javascript">
window.addEventListener("DOMContentLoaded", function () { 
  (function($) {
    $('.avia-content-slider-inner .slide-entry-wrap .slide-entry').each( function() {
        $(this).detach().appendTo('.avia-content-slider-inner .slide-entry-wrap:first');
    });
    $('.avia-content-slider-inner .slide-entry-wrap:empty').remove();
  })(jQuery);
});
</script>
<?php
}
add_action('wp_footer', 'wrap_articles_in_one_flex_container');

And then style that one wrapper f.e. with flexbox layout on quick css:

#top .avia-content-slider .slide-entry-wrap {
  display: flex;
  flex-flow: row wrap;
  justify-content: space-between;
}

#top.blog .slide-entry::before, 
#top.blog .slide-entry::after {
  display: none;
}

#top .avia-content-slider .slide-entry-wrap .slide-entry {
  flex: 0 1 calc(33% - 30px) ;
  margin: 0px 15px 30px !important;
  width: unset !important;
  padding: 0px !important;
}

@media only screen and (max-width:989px) {
  #top .avia-content-slider .slide-entry-wrap .slide-entry {
    flex: 0 1 calc(50% - 30px);
    margin: 0px 15px 30px !important;
  }
}

@media only screen and (max-width:767px) {
  #top .avia-content-slider .slide-entry-wrap .slide-entry {
    flex: 0 1 100%;
    margin-bottom: 30px !important;
  }
}

see here : https://webers-testseite.de/blog/

One thing to mention: a paginated blog will not work correctly that way – because the amount of entries each page will not be influenced.

PS: On the example page of enfold there is an audio entry – and on this one the width calculation does not work because of a setting by Enfold. On this page it would be necessary to set the width:

#top .avia-content-slider .slide-entry-wrap .slide-entry .mejs-container {
  min-width: unset !important;
  width: unset !important;
}

Yes on mobile devices – it is ok – but click on hamburger on desktop browsers! ( screens bigger than 768px)

Now: see f.e. that page and its curtain effect footer: https://enfold.webers-webdesign.de/

The content of that footer will end on small screens ( all columns are beneath each other ) at a height of 1176px.
So even if i could set that option when curtain effect footer goes to scroll to 100% ( only 90% option is available ) there will be no space to show all the content on f.e. an iPhone 11 ( screen-height is : 812px) – so if that footer stays on fixed position there will be 364px that could not be seen.
The only way to see the whole footer content is then to set position to relative and scroll with the content !

if we are talking about your homepage ( link on your nick) The footer is still fixed on my mobile devices.
but for mobile devices with less than 736px ( iPhone 6,7,8) it will scroll – because:
your footer height will be on that screenwidth of 375px : 535px and this is nearby 80% of available screen-height. That is the reason why i give you the snippet to enlarge the allowed footer height to set to 90%.
In this case your footer will be even fixed on Mobiles with 736px screen
if you got iPhone 5 it is 568px available – no chance even on 90% to have a fixed footer with curtain effect.

so look again to the example page: https://webers-web.info/

This is default behavior on transparency pages – showing first the logo (from options : header – transprency options – transparency logo) after shrinking finished the default logo is shown.

And that is what you like to have on all pages – even those with header option : not transprency.

Your topic of that is the way i understand – different logo during scrolling – stop scrolling default logo:

the method used for your aim depends on the logos you like to use.
E.g. – Logo a and logo b are only colored differently (change of font color – change of branding color etc.). I would try to realize it by an svg logo just switching the fill colors by scroll event.
Etc.

F.e. two logo variants are by same dimensions. Insert your logo as usual – and set on quick css the other logo as background-image.
on my example page these are svg files – but png or jpg is also a possibility.

.av-contains-svg.invisible  {
  background-image: url(/wp-content/uploads/icon807.svg);
  background-repeat: no-repeat;
  background-size: contain;
  background-position: center center;
}

.av-contains-svg.invisible svg {
  opacity: 0;
  transition: opacity 1s ease-in-out
}

the jQuery function now on child-theme functions.php:

function invisible_on_scrolling() { 
?>
<script type="text/javascript">
(function($){
  let timeout;
  let $targetOnScroll = $('.av-contains-svg');

  $(document).on("scroll", () => {
    $targetOnScroll.addClass("invisible");
    clearTimeout(timeout);
    timeout = setTimeout(() => $targetOnScroll.removeClass('invisible'), 200);
  });
})(jQuery);
</script>
<?php 
}
add_action('wp_footer', 'invisible_on_scrolling');

see: https://webers-web.info/datenschutz/

Or: do you like to have different logo during shrink – after shrink finished – default logo
can you link to my post that you are referring to?