on your example page – where is there a background video autoplaying ?

Edit: i found on top of work page a background-video:
see source-code: ( click to enlarge )

as a cdn hosted video – it is a kind of self-hosted video. ( not a youtube nor vimeo etc. ) but html5 video.
These videos can be played even inline on mobile devices – with autoplay option.

see here on your mobile device: https://webers-webdesign.de/
on my page this was a small video – so i selfhost it.
but with bigger videos – a cdn is very helpful. – til 100mb you might use cloudinary free cdn

test it by yourself – insert the video source of that page to your color-section background:
https://cdn.sidlee.com/-/media/sidlee/work/hero_video/web_loop_work.mp4

no the point is what i said above: the magnific popup js ( jquery.magnific-popup.min.js ) is not loaded
and there must be a reason for it. Best would be that a mod will look into your installation.

i prefere to write the whole script a $ instead of jQuery – makes some things easier to understand.

try:

function ava_move_meta_after_title(){ 
?>
<script>
(function($){
	$('.slide-entry').each(function() {
		var metaInfo = $(this).find('.slide-meta');
		var postTitle =  $(this).find('.entry-content-header');
		metaInfo.insertBefore($(postTitle));
	});
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'ava_move_meta_after_title');

no – only header.php has some entries for lightbox use.

you are not using a child-theme – where did you place those snippets ?

that script is ok – and you changed it to on(‘load’ … that is totally correct here – because former load is now deprecated on jQuery 3.5.1

the magnific popup js ( jquery.magnific-popup.min.js ) is not loaded – maybe a plugin that hampers loading it ?

again btw:
you can extend this shortcode by f.e.:

function show_date_with_shortcode() { 
  date_default_timezone_set('Europe/Berlin');
  setlocale(LC_TIME, 'de_DE.UTF-8');
  $uhrzeit = date_i18n( 'l, \d\e\n ' . get_option( 'date_format' ) . ' ' . get_option( 'time_format' ). ' \U\h\r'  );
  return $uhrzeit ;
}
add_shortcode( 'show-date', 'show_date_with_shortcode' );

shortcode is then : [show-date]

the get option is concerning to that what you have set on Dashboard – Settings – General : “Date Format” and “Time format”

you see the timezone setting and if there must be binding words the letters had to be escaped
f.e. on german “Uhr” for hour and “den” for the may the fourth be with you :lol

see here in the socket: https://webers-testseite.de/pureinstall/#socket

i always do updates by this : https://kriesi.at/support/topic/some-hints-and-advice-to-update-enfold/#post-1056107

the rename method this way gives you the opportunity to go back if something went wrong.
The downtime is minimal if something should not work.

yes that would be ok – if there was no margin between the columns.
but second and third column got a margin-left of 6% – so for your columns in total there are only 88%
so try 22% 22% and 44%

or if you can live with less space between the columns:

@media only screen and (min-width: 768px) {
  #footer .flex_column.av_one_third:nth-child(1) {
    width: 24%;
  }
  #footer .flex_column.av_one_third:nth-child(2) {
    width: 24%;
    margin-left:3%
  }
  #footer .flex_column.av_one_third:nth-child(3) {
    width: 46%;
    margin-left:3%
  }
}

Da muss was mit deiner Seite nicht gänzlich in Ordnung sein.

Ich bekomme keine reproduzierbaren Seitendarstellungen hin.
Soll bedeuten: Wenn ich in den Browsercache komplett lösche z.B. mittels Tastenkombination in Firefox:

• «ctrl + shift + r» (Windows)
• «command + shift + r» (Mac)

dann sieht es mal so auch – mal anders. ( halbe bilder im slider oder in der erwähnten tab-section ; logo mal ganz links dann wieder nicht etc. pp )
Da musst du mal nachforschen woran das liegen könnte.

_____________________

There must be something wrong with your page.

I can’t get a reproducible page display.
This should mean: If I delete the browser cache completely, e.g. using the key combination in Firefox:

• “ctrl + shift + r” (Windows)
• “command + shift + r” (Mac)

then it looks sometimes like this – sometimes different. ( half images in the slider or in the mentioned tab-section ; logo sometimes all the way to the left then again not etc. pp )
You’ll have to investigate what that could be.

for every single cell you can have a background-image – but the whole grid-row element doesn’t have that feature.
( on options dialogs ) on quick css you can set this aswell.

On the alb options of your columns – you had to choose “no space between columns”
Then on quick css:

#top #fullwidthsection .container {
    max-width: 100%;
    width: 100%;
    padding: 0;
}

see here: https://webers-testseite.de/color-section-full-width-container/

if it is important for you that on responsive case the columns are without space and the full-width is still there:

@media only screen and (max-width: 767px) { 
  .responsive #top #wrap_all #fullwidthsection .container {
    width: 100%;
    max-width: 100%;
  }
  .responsive #top #wrap_all #fullwidthsection .container .flex_column {
    margin-bottom: 0
  }
}

for the slider …

.avia-slideshow-dots a {
  height: 25px;
  width: 25px;
  border-radius: 50%;
  margin: 0 5px;
  padding: 5px;
}

for the tab section:

#top .av-tab-section-icon:before {
    font-size: 90px !important; 
}

ich habe das eben an dem neuesten Enfold getestet. Bei mir geht das
Wenn ich dann in die Kategorien wechsle danach, erscheint folgende Warnung ( da meine Testumgebung in Englisch ist ):

meine Befürchtung war das auch die Items – also die Einzelbeiträge in der Kategorie gelöscht sind- erwies sich als nicht richtig.
Diese Beiträge bekamen dann die Standard Kategorie zugeteilt.

see here a demo with code : https://webers-testseite.de/gallery-with-8-images/

if you like to have those images on the left side on break ( see 3/3/2 )
change that rule to:

.flexed-gallery .avia-gallery-thumb {
    display: flex !important;
    flex-flow: row wrap;
    justify-content: flex-start;
}