For Oxygen Builder Go to Top smooth scroll effect, use below snippet

add_action('wp_footer', function() {
?>
<script>
jQuery(document).ready(function($){
 
    // Change selector to match your button class or ID
    $('.oxel_back_to_top_container').click(function(e){
        e.preventDefault();
 
        $('html, body').stop().animate({
            scrollTop: 0
        }, 500); // 👈 Adjust speed here (1000 = smooth)
 
    });
 
});
</script>
<?php
});