unmute background video

Hi
On the site below I have a background video in a color section at the bottom of the page.
I added an unmute button to the video, and it seems to be working.
I added the codes I found here: https://kriesi.at/support/topic/html-for-turning-on-audio/#post-1432783
and on this page: https://webers-testseite.de/mute-unmute/

I didn’t understand where to place the first code where it says :
Activate Child-theme shortcodes replacement by:

add_filter('avia_load_shortcodes', 'avia_include_shortcode_template', 15, 1);
function avia_include_shortcode_template($paths){
  $template_url = get_stylesheet_directory();
      array_unshift($paths, $template_url.'/shortcodes/');
  return $paths;
}

Do I add that to my functions.php or is it OK as it is?

I am also still seeing the mute icon on mobile, even though my css is:

@media only screen and (min-width: 768px) {
.custom-mute {
    display: block;
    background-image: url('/wp-content/uploads/2025/08/icon-mute.png');
    background-size: cover;
    width: 50px;
    height: 50px;
    position: absolute;
    bottom: 8%;
    right: 4%;
    z-index: 50;
}
.custom-mute:hover {
	opacity: 0.7;
}
.icon-sound-on {
	background-image: url('/wp-content/uploads/2025/08/icon-sound.png');
}}

can you help me with this?

thanks
Nancy

• This topic was modified 1 day, 4 hours ago by Munford.
• This topic was modified 1 day, 2 hours ago by Munford.
• This topic was modified 1 day, 2 hours ago by Munford.
• This topic was modified 1 day, 1 hour ago by Munford.