Hi Kharis,
Thank you so much for your support.
Unfortunately, I was unable to get this code to work, but now I got the wanted behavior using this string:
jQuery('.menu-item').on( "click", function() {jQuery('#mainnav-mobi').hide()})
Also thanks for the suggested plugin. Since I am already using the Advanced Ads plugin I also implemented this custom footer code injection with it. Works like a charm.
All the best!
BW