For Responsive menu add this js in header

<script src="<?php echo get_template_directory_uri(); ?>/js/jquery.slicknav.js" type="text/javascript"></script>

<script type="text/javascript">

jQuery( document ).ready(function( $ ) {
$('#mainnav-menu').slicknav();
// Code that uses jQuery's $ can follow here.
});
</script>