Copy-Paste This custom code before body (After jquery loaded) under page setting (For specific page) or under site setting (For entire site).
<!-- Jquery: Close webflow Nav on click -->
<script>
$('.w-nav-menu').on('click', 'a', function() {
$('.w-nav-button').triggerHandler('tap');
});
</script>
And publish the site. Reference for the code: