we can surround the weekday by some html with a class. Those extra letters had to be escaped.

Replace the whole code with:

function add_date_time_popup_content( $content ) {
	if ( ! function_exists( 'pum_get_popup_id' ) ) return;
	$popup_id = pum_get_popup_id();
	return "<p class='date-published'>" . get_the_date( '\<\s\p\a\n \c\l\a\s\s\=\"\w\e\e\k\d\a\y\"\> l \<\/\s\p\a\n\> \d. d.m.Y' , $popup_id ) . "</p>" . $content  ;
}
add_filter( 'pum_popup_content', 'add_date_time_popup_content' );

function show_date_of_popup(){
?>
<script type="text/javascript">	
(function($) {
	$(document).ready(function(){ 	  
		$('.pum-trigger').each(function() {
			var pumPopup = $('.pum').css('display');
			var trigger_name = $(this).attr('class').split(' ')[0];
			var publishingDate = $(this).closest('#top').find('#'+trigger_name+' .date-published').html();
			var date_published = $('<span class="puplished">'+publishingDate+'</span>');
			$(this).append(date_published);	
		});
	});	
})(jQuery);	       
</script>
<?php
}
add_action('wp_footer', 'show_date_of_popup', 9999);

and put this to quick css:

.puplished .weekday,
.date-published .weekday {
	text-transform: capitalize;
}

EDIT: sorry didn’t see that you like to have that as popup – so read the next Answer
___________________
But if your visitors want to navigate further on your page – how do you want to offer that?

you can place a button for instance that will go back in browser history – just place a button and give a custum-class to it: goback
this to child-theme functions.php:

function go_back_button(){
?>
<script type = "text/javascript">
(function($){
  $('.goback').on('click', function(e){
      e.preventDefault();
      window.history.back();
  });
})(jQuery);
</script>
<?php
}
add_action( 'wp_footer', 'go_back_button' );

if you like to have some binding words in that date do it this way:
The backslash will show the code that it does not stand for the day but to have text here

'l \d. d.m.Y'

first you told me it is too long!

Replace the part of the function above:

function add_date_time_popup_content( $content ) {
	if ( ! function_exists( 'pum_get_popup_id' ) ) return;
	$popup_id = pum_get_popup_id();
	return "<p class='date-published'>" . get_the_date( 'l, d.m.Y' , $popup_id ) . "</p>" . $content  ;
}
add_filter( 'pum_popup_content', 'add_date_time_popup_content' );

that part: ‘l, d.m.Y’ is responsible for it:
see here foramting options: https://wordpress.org/support/article/formatting-date-and-time/

• This reply was modified 4 years, 7 months ago by Guenni007.

this in the code above

var trigger_name = $(this).attr('class').split(' ')[0]

will search for the classes – split the class list on spaces and will take the first class ( it starts at 0 )

this is what i got on the test:
( click to enlarge )

i got the id at the second position !

yes sorry – on my testinstallation i have first the pum-trigger class than the id
so i corrected the second code to split on [0]
( var trigger_name = $(this).attr('class').split(' ')[0]; this is different to my installation – you had to take the first part of the class list )

replace it

here is the solution to it:

remove the shortcode function so that you only have on child-theme functions.php:

// this is now the code to insert the popup publishing date - 
// all credits goes to a guy that helped me from wp-popupmaker : Mark Chaves !
function add_date_time_popup_content( $content ) {
	if ( ! function_exists( 'pum_get_popup_id' ) ) return;
	$popup_id = pum_get_popup_id();
	return "<p class='date-published'>" . get_the_date( 'd.m.Y' , $popup_id ) . "</p>" . $content  ;
}
add_filter( 'pum_popup_content', 'add_date_time_popup_content' );

//-----------------
// this is the known script
function show_date_of_popup(){
?>
<script type="text/javascript">	
(function($) {
	$(document).ready(function(){ 	  
		$('.pum-trigger').each(function() {
			var pumPopup = $('.pum').css('display');
			var trigger_name = $(this).attr('class').split(' ')[0];
			var publishingDate = $(this).closest('#top').find('#'+trigger_name+' .date-published').text();
			var date_published = $('<span class="puplished">'+publishingDate+'</span>');
			$(this).append(date_published);	
		});
	});	
})(jQuery);	       
</script>
<?php
}
add_action('wp_footer', 'show_date_of_popup', 9999);

here is a layout made for another participant : https://webers-testseite.de/steviger/

The Reverse Order is only to have the second column ( with that navigation in it ) on top in responsive case.

it correlates with scroll speed – so no animation / transition speed here.
Slower scrolling is the solution

or if you like this – maybe it is a satisfiing solution for you:

#top #header,
#top .av-logo-container ,
#top #header .av-main-nav > li > a,
.logo a, 
.logo a img {
  transition: all 3s ease !important;
}

Different Approach
Wenn wir die Pfeile innerhalb des content containers setzen laufen Sie ja mit der Verschiebung.
Dazu müsstest du dies hier in die child-theme functions.php setzen:

function popup_arrows_change() { 
?>
<script type="text/javascript">
(function($){
$(window).on('load', function(){
    $('.av-masonry-entry.lightbox-added').magnificPopup({ 
	    type: 'image',
	    mainClass: 'avia-popup mfp-zoom-in mfp-image-loaded',
	    closeOnContentClick: false,
	    midClick: true,

	    gallery: {
	      enabled: true
	    },

	    callbacks: {
	      buildControls: function() {
	        // re-appends controls inside the main container
	        this.arrowLeft.appendTo(this.contentContainer);
	        this.arrowRight.appendTo(this.contentContainer);
	      },
	    },

  	}); 
});
})(jQuery);
</script>
<?php }
add_action('wp_footer', 'popup_arrows_change');

und das ins quick css:

.mfp-arrow {
  margin: 0 -90px;
  margin-top: -55px;
}

.mfp-arrow:active {
    margin-top: -55px;
}

ABER: Wichtiger – richtiger wäre den Fehler zu finden.

welche Header Variante hast du gewählt?
bei normalen Header ( Logo im Kopfzeilenbereich – unter Enfold – Allgemeines Layout – “Logo und Hauptmenü” ) – sind die ausgeblendet:

.avia-menu-subtext {
	display:none;
}

wenn du die auf display : block setzt, werden sie angezeigt. – Die musst du dann nur noch stylen, denn viel platz ist ja nicht da.
Ist aber bei z.B. einem shrinking header nicht trivial !

Das ist eigentlich so wie Rikard oben schon anmerkte mit dem Link – nur bei “Sidebar links oder rechts” gedacht

Please switch off the merging of the js and css files anyway, then it will be easier for us to find the possible errors in the css.

Enfold (Child) – Leistung – “…Datei-Zusammenführung und -Komprimierung”

zudem musst du unbedingt etwas an deinen DSGVO Einstellungen ändern.
Ohne dass ich auf deiner Seite etwas geantwortet habe – oder schlimmer noch indem ich nur notwenigen Cookies zustimmte, wird google analytics und google tag manager geladen ( schrift lato ohnehin auch )
Wenn unsere Kollegen hier aus dem internationalen Ausland das machen ok, aber wir in Deutschland ( oder EU ) müssen uns daran streng halten ohne Opt-In hier nichts zuzulassen.
Deine Seite ist höchst abmahn-gefährdet deshalb.

when you hover on dashboard your CPT “Categories” what is shown on your browser for taxonomie as you can see here by portfolio:

this is the analogon in your code above – if it is as you suspect: publication_post
try:

function avf_change_which_archive($output){
	$term = get_term_by( 'slug', get_query_var( 'term' ), get_query_var( 'taxonomy' ) );
		if(is_tax('publication_post')){
			$output = __('Search for:','avia_framework')." ".$term->name; 
		} 
		else {
			$output = __('Archive for:','avia_framework')." ".$term->name; 
		}
	return $output;
}
add_filter('avf_which_archive_output','avf_change_which_archive', 10, 3);

Till a solution is found you can place the publishing date manually to your popups as:

<span class="date-published">xx.xx.2021</span>

The date will than be inserted automatically to your list.

See here : https://wordpress.org/support/topic/echo-get_the_date-in-popup-window/