do these buttons have always the same link? or is it an individual link?

try Mikes Solution – did not know why the content-slider.php does not rule that – see next post

try instead:
these are the bold versions

function avia_replace_default_icons($icons){
 $icons['svg__scrolldown'] =  array( 'font' =>'svg_entypo-fontello', 'icon' => 'down-open');
 $icons['svg__prev'] =  array( 'font' =>'svg_entypo-fontello', 'icon' => 'left-open');
 $icons['svg__next'] =  array( 'font' =>'svg_entypo-fontello', 'icon' => 'right-open');
 return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

ok – but even if you like to replace those icons:

.carousel-slider.arrows-outside .owl-nav svg {
  display: none
}

.carousel-slider.arrows-outside .owl-nav .owl-prev:before,
.carousel-slider.arrows-outside .owl-nav .owl-next:before {
  font-family: 'entypo-fontello';
  font-size: 52px;
}

.carousel-slider.arrows-outside .owl-nav .owl-next:before {
  content: "\E875";
}

.carousel-slider.arrows-outside .owl-nav .owl-prev:before {
  content: "\E874";
}

now the other ones …

btw. i do not see if you have set this rule yourself ( merged styles ):

@media only screen and (min-width: 485px) and (max-width: 1023px) {
  .html_av-submenu-hidden .av-submenu-indicator {
    margin-right: 175px;
    opacity: 100% !important;
    font-weight: bold !important;
  }
}

the margin-right value causes the icon to be overlaid with the text.

or – if you like to replace it by a different svg graphic – you can do it by an uploaded graphic to media-library:

function avia_replace_default_icons($icons){
 $icons['svg__scrolldown'] =  array( 'font' =>'svg_wp-media-library', 'icon' => '50913');
 return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

change the icon ID to your file id

____________________________________________________________________________________________________
you can find the attachment-ID best in media-library list-view –
or in grid-view if you open the attachment-details ( look to the url that is opened )

or the arrow thought even more demanding ;)

:root {
  --burger-main-icon-width: 40px; /* === adjust to your needs === */
}

@media only screen and (max-width:1150px) {
  .av-hamburger {display: none}

  #header #avia-menu li.av-burger-menu-main.menu-item-avia-special,
  #top #wrap_all #header .av-small-burger-icon a:before{
    width: var(--burger-main-icon-width);  
  }
  
  #top #wrap_all #header .av-small-burger-icon a {
    display: flex; 
    justify-content: center;
    align-content: center;
    align-items: center;
  }

  #top #wrap_all #header .av-small-burger-icon a:before {
    content: "\e873";
    font-family: "entypo-fontello";
    font-size: var(--burger-main-icon-width);  
    color: var(--enfold-main-color-primary);
    text-align: center;
  }

  .av-burger-overlay-active #top #wrap_all #header .av-small-burger-icon a:before{
    font-size: calc(1.5 * var(--burger-main-icon-width));  /* === only if you like it === */
    color: #FFF;
    content: "\e877 \A \e873";
    line-height: 0.35em;
    animation: avia_fade_move_down 2s ease-in-out infinite;
  }
}

on my installation it works without any problem – if you use the webp images from media-library!
https://webers-testseite.de/webp-lightbox/

or: next suggestion – you are using a plugin that replaces jpgs by webp images ( f.e. from shortpixel – automatic calculation of jpgs to webp- and replacement in DOM )

As mentioned above

var defaults = {
	groups :	['.avia-slideshow', '.avia-gallery', '.av-horizontal-gallery', '.av-instagram-pics', '.portfolio-preview-image', '.portfolio-preview-content', '.isotope', '.post-entry', '.sidebar', '#main', '.main_menu', '.woocommerce-product-gallery'],
	autolinkElements : 'a.lightbox, a[rel^="prettyPhoto"], a[rel^="lightbox"], a[href$=jpg], a[href$=webp], a[href$=png], a[href$=gif], a[href$=jpeg], a[href*=".jpg?"], a[href*=".png?"], a[href*=".gif?"], a[href*=".jpeg?"], a[href$=".mov"] , a[href$=".swf"] , a:regex(href, .vimeo\.com/[0-9]) , a[href*="youtube.com/watch"] , a[href*="youtube.com/shorts"] , a[href*="screenr.com"], a[href*="iframe=true"]',
	videoElements  : 'a[href$=".mov"] , a[href$=".swf"] , a:regex(href, .vimeo\.com/[0-9]) , a[href*="youtube.com/watch"] , a[href*="youtube.com/shorts"] , a[href*="screenr.com"], a[href*="iframe=true"]',
	exclude  :	'.noLightbox, .noLightbox a, .fakeLightbox, .lightbox-added, a[href*="dropbox.com"], .pagination a'
},

a[href$=webp] is an autolinkElement – so there must be something that hampers this on your installation.

ok – you are right that on that icon the down-open-mini is used ! – you can change it by code snippet inside your child-theme functions.php:

function avia_replace_default_icons($icons){
 $icons['svg__scrolldown'] =  array( 'font' =>'svg_entypo-fontello', 'icon' => 'down-open');
 return $icons;
}
add_filter('avf_default_icons','avia_replace_default_icons', 10, 1);

you find those settings including the filter in init-base-data.php
there you see that the scrolldown icon is correlated with the down-open-mini svg.

charmap can be found in: charmap-svg.php

Isn’t it just a question of size? Wouldn’t specifying the width/height alone lead to the same result?
PS: in your case you are already use the svg icons. if someone uses the font-icons the snippet will be different –
and correlation is on default by:
'scrolldown' => array( 'font' => 'entypo-fontello', 'icon' => 'ue877' ),

try f.e.:

#top .scroll-down-link {
  height: 50px;
  width: 50px;
  bottom: 50px;
  background-color: rgba(255,255,255,0.3);
  border: 1px solid var(--enfold-socket-color-border);
  backdrop-filter: blur(4px);
  border-radius: 10px;
  /*** animation: none; ***/
}
#top .scroll-down-link.avia-svg-icon svg:first-child {
  height: 50px;
}

#top .scroll-down-link:hover {
  background-color: rgba(255,255,255,0.8);
}

#top .scroll-down-link svg path {
  fill: var(--enfold-main-color-primary);
}

if you do not like the animation – just get rid of the outcommenting /*** ***/

try the code-block element instead – be shure you have choosen on advanced tab “Add Codeblock to content”

i think google likes to see an aria-label on that links.

function ava_script_mod() {
?>
<script type="text/javascript">
jQuery(function($){
  $('.scroll-down-link').each(function() {
    $(this).attr('aria-label', 'Passer à la section suivante');
  });
});
</script>
<?php
}
add_action( 'wp_footer', 'ava_script_mod', 9999 );

by the way this:

jQuery(function($){
// is shorthand for 
jQuery(document).ready(function($) {

At the very least, it would be good to know your header settings (logo left, menu below, etc.). For example, when I work on the new version with (logo left, menu right), the social bookmarks are located within main_menu. When I look at the board at the top here, they are located next to main_menu. – That depends on where I place the flex container.

so it all depends on your setting . so it will be the best to see the concerning site.

f.e. if you got a setting that the burger is visible from the beginning – like in freelancer demo

then you had to remove the media-query setting for screens above 768px.

try

@media only screen and (max-width: 989px) {
  .responsive #top #wrap_all .main_menu {
    display: flex !important;
    flex-direction: row-reverse;
    align-items: flex-start;
    height: 100% !important;
  }
  #top #wrap_all .social_bookmarks {
    padding-right: 20px;
    border-right: 1px solid var(--enfold-header-color-meta);
  }
}

@media only screen and (min-width: 768px) and (max-width: 989px) {
  .responsive.html_mobile_menu_tablet #top .avia-menu.av_menu_icon_beside {
    border: none;
    padding-right: 0px;
  }
}

@media only screen and (max-width: 767px) {
  .responsive #top #wrap_all #header .main_menu > .social_bookmarks {
    display: block !important;
    top: 40px
  }
  .responsive #top #wrap_all .av_mobile_menu_tablet .main_menu {
    align-items: flex-start;
  }
  .responsive #top .av_seperator_big_border .avia-menu.av_menu_icon_beside {
    padding-right: 0;
    margin-right: 0;
    border: none;
  }
}

and check please the style on screens less than 767px if that fits for you. on medical demo it works well.