How do I create a Button to scroll down

Scroll down to what position ? Footer ?

if you do not need the scroll to top button – just use that for your needs
it has an absolute position so you can shift him anywhere you like:

#scroll-top-link {
  right: inherit;
  bottom: inherit;
  left: 20px;
  top: 90px;
}

#scroll-top-link::before {
  content: "\e87b";
}

the second rule changes that arrow to an arrow down!

now the link if you link to the #socket ( otherwise give a link target your want on that page – best would be a unique ID )
do this to your child-theme functions.php:

function change_href_of_scroll_top_link(){
?>
<script>
(function($) {
  $('#scroll-top-link').attr("href", "#socket");
  $('#scroll-top-link').attr("title", "Scroll to bottom")
  $('.avia_hidden_link_text').text('Scroll to bottom');
})(jQuery);
</script>
<?php
}
add_action('wp_footer', 'change_href_of_scroll_top_link');

Now the only thing is that the button appears the same manner like the scroll to top button ( after some scrolling) this could be changed too.