The functions.php is located directly in the root directory of the theme. However, if you are working without a child theme, there are a few things to consider for the parent theme. That’s why I recommend always working with a child theme: changed settings / customizations will not be lost with the next update.

or – instead of replacing it afterwards – use the filter avf_customize_heading_settings to influence the generation of those headings:

function my_customized_headings_for_masonry_titles( array $args, $context, array $extra_args = array() ) {
  if( $context == 'avia_masonry' ){
    $args['heading'] = 'h6';             
  }
  return $args;
}
add_filter( 'avf_customize_heading_settings', 'my_customized_headings_for_masonry_titles', 10, 3 );

It’s good that one can always check the corresponding pages to see if it worked. ;)

on docu – you can find a possibility not to use for those images a different source :
see https://kriesi.at/documentation/enfold/magazine/ and search for: image_size

maybe we can use the avf_magazine_defaults filter to change that. … ;)
put this to your child-theme functions.php:

function avia_magazine_thumbnail($atts, $magazine){
	$atts['image_size']['small'] = 'square';
	return $atts;
}
add_filter('avf_magazine_settings', 'avia_magazine_thumbnail', 10, 2);

if you got a link on your private Content field – i could not see this as participant.
So maybe a mod should adjust it for you.

btw: if you got the hamburger icon from the beginning the media query aren’t needed!

you can put inside the same media query to have then complete:

@media only screen and (max-width:989px) {
  .responsive #top .av-burger-menu-main  {
    top: -5px
  }
  #top .av-burger-menu-main .av-hamburger-box strong {
    display: block !important;
    position: absolute;
    top: -10px;
    left: 50%;
    transform: translateX(-50%);
    color: var(--enfold-header_burger_color); 
  }
  #top #header.av_header_transparency .av-burger-menu-main .av-hamburger-box strong {
    color: var(--enfold-header_replacement_menu_color); 
  }
}

colors if burger menu is active – f.e.:

#top .header_color .av-hamburger--spin.is-active .av-hamburger-inner, 
#top .header_color .av-hamburger--spin.is-active .av-hamburger-inner::before, 
#top .header_color .av-hamburger--spin.is-active .av-hamburger-inner::after{
  background-color: #FFF;
}

#top .av-burger-menu-main .av-hamburger--spin.is-active .av-hamburger-box strong {
  color: #FFF ;
}

can you try this:

#top #header .avia_mega_div {
  max-height: calc(100vh - 20px);
  overflow-y: auto !important;
}

That exactly is the meaning of background-images. The content height determins the height of the section.

by the way – it now makes me wonder that the original inline rule set by Enfold is with height and not min-height:

.av-minimum-height-90:not(.av-slideshow-section) .container {
  height: 90vh;
}

so my code above reflects that.
Try first now to set only a min-height to 50vh

But as mentioned : the content height will be the determinating factor on that.

give a custom class to your color-section – f.e. : fifty

then put your rules inside a media-query: ( if you like to have it on a different screen-width than 767px – change that f.e. to 989px )

@media only screen and (max-width:767px) {
  .responsive #top .avia-section.fifty {
    height: 50vh;
  }
}

PS: if you really like to have that only for mobile devices – and not for small screen sizes ? you can change that selector ( and use the enfold default class for mobile devices: avia_mobile ):

.responsive.avia_mobile #top .avia-section.fifty {
  height: 50vh;
}

but if I then open one of the two portfolio entries I can scroll to the other entry

you belong to the post navigation arrows left and right. If those entries should stay only in the same category …
can you try this in your child-theme functions.php:

add_filter('avf_post_nav_settings','enfold_customization_postnav', 10, 1);
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);

if it does not work . we can try a different way …

Well – there is a free version too – but i can not say if this is the plugin you use.
For a customer – long time ago – i edited the postslider.php to insert the counter into meta info of a post.
But I would have to think my way back into it first; the version of postslider.php I still have saved here is from 2020
maybe loop-index.php should also be edited.

i think only a code like this :

number_format_i18n(pvc_get_post_views( $the_id ))

had to be inserted to the $meta.

F.e. open loop-index.php and find around line 431:
$meta_seperator = apply_filters( 'avf_post_metadata_seperator', '<span class="text-sep">/</span>', 'loop-index' );

place just under that line:

$meta_postviews  = "<span class='post-views' title='Calls for: ".get_the_title( $the_id )."'><span class='post-views-icon dashicons dashicons-businessperson'></span>".number_format_i18n(pvc_get_post_views( $the_id ))."</span>";
$meta_info['postviews'] = $meta_postviews;

upload that edited loop-index.php to a child-theme folder : includes

see how it looks like ( after a short css )
https://weber.tips/clock/

on fontello – uploading those svg files – there are no error warnings? Did you see those uploaded icons in the preview on fontello?

one hook that might help is : tiny_mce_before_init

what do you like to have added?

oh wow – did not see that you are only asking for the logo hide/show !
so forget about my solution – which is meant for hide/show complete header – sorry

and if you like to have the benefit of those classes added on scroll – without having a shrink see:

https://kriesi.at/support/topic/how-to-set-a-very-small-shrink-factor/#post-1416772

oh wow – did not see that you are only asking for the logo hide/show !
so forget about my solution – which is meant for hide/show complete header – sorry

_________ so this is not for your problem ____________

yes, this is a possibility – but has the disadvantage that this class (header-scrolled) is only removed if you are in the top position on the page. This means that the header only appears again then. If you scroll-direction is up at the bottom (or middle) of a page, nothing happens.
It would therefore be better to have a class that is removed as soon as a certain distance is scrolled back – and thus restores the header visibility.

This is a function adding a class (hide-header) depending on scroll distance.

function hide_header(){
?>
<script>
(function($){

  'use strict';
  var c, 
  currentScrollTop = 0,
  header = $('#header');

   $(window).on('scroll', function () {
      var a = $(window).scrollTop();
      var b = header.height();
      currentScrollTop = a;

      if (c < currentScrollTop && a > b  ) {
        header.addClass("hide-header");
      } else if (c > currentScrollTop && !(a <= b)) {
        header.removeClass("hide-header");
      }
      c = currentScrollTop;
  });
})(jQuery);   
</script>
<?php
}
add_action('wp_footer', 'hide_header');

The css you need on that must reflect your header height you set on Enfold options. And the options – f.e. if you have a top-menu or phone-info field above the header. And if it scrolls away.

The trick now is to shift the header in y-direction above the viewport.
And because we do not want to do that if the burger menu is opend – we exclaim it bei not selector ( :not(.av-burger-overlay-active) )
The media query settings are individual – and you have to adjust it to your needs – if you got pages with transparency headers – maybe there had to be different padding-top settings of #main.

css – first settings:

.responsive:not(.av-burger-overlay-active) #header {
  top: 0px;
  -webkit-transition: transform 0.5s ease-in;
  transition: transform 0.5s ease-in;
}

.responsive:not(.av-burger-overlay-active) #header.hide-header {
  -webkit-transition: transform 0.5s ease-in;
  transition: transform 0.5s ease-in;
}

.responsive:not(.av-burger-overlay-active) #main {
  top: 0px;
  -webkit-transition: padding-top 0.5s ease-in;
  transition: padding-top 0.5s ease-in;
}

.responsive.av-burger-overlay-active #header {
  position: fixed !important;
}

@media only screen and (min-width: 990px) {
  .responsive:not(.av-burger-overlay-active) #header.hide-header {
     transform: translateY(-116px);
  }
}

@media only screen and (min-width: 768px) and (max-width: 989px) {
  .responsive:not(.av-burger-overlay-active) #header {
    position: fixed !important;
    top: 0;
  }
  .responsive:not(.av-burger-overlay-active) #header.hide-header {
     transform: translateY(-90px);
  }
  .responsive #top #main {
     padding-top: 90px !important;
  }
}

@media only screen and (max-width: 767px) {
  .responsive:not(.av-burger-overlay-active) #header {
    position: fixed !important;
    top: 0;
  }
  .responsive:not(.av-burger-overlay-active) #header.hide-header {
     transform: translateY(-80px);
  }
  .responsive #top #main {
     padding-top: 80px !important;
  }
}

After activating the Debug Mode the shortcodes shown under the layout insertion field.:

copy all shortcodes from there and input these to the same field in a new created page on the other installation.
And save now.
After that you had to fix the content – as the links, e.g. from images, still point to the first domain.