Help Jones template

Hi, I've posted this a few times but i haven't received any help, I've sent emails to square space staff and have asked multiple times on this forum but i haven't received any feedback.  I'm not sure if i'll still want to use Squarespace to host my site, since frankly the templates all have something that cant be adjusted or is frankly annoying.  

None the experts have helped and I've sent my password and link to people and I've received NO help at all.  I'm asking one last time before i switch services if anyone is here is willing to help me.  I'm frankly fucking pissed of and aggravated that i'm willing just say fuck it and switch over.

Here is what i'm looking for.

Current template that I'm Using: Jones Template

1.  Keep the main header Fixed - when i scroll I want it to stay fixed

2.  In the mobile menu - when expanding the list items get blocked by the top menu bar and it keeps me from collapsing it.  I need help to keep the fucking menu from not going past the top menu bar so you can collapse the fucking thing.  

ANYONE?!

Q1. Add to Home > Settings > Advanced > Code Injection > Header

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.5.0/jquery.min.js"></script>
<script>
$(function(){
 var visibleTop = 10;
  $(window).scroll(function() {
    var scroll = getCurrentScroll();
      if ( scroll >= visibleTop ) {
           $('header#header').addClass('tuan');
        }
        else {
            $('header#header').removeClass('tuan');
        }
  });
function getCurrentScroll() {
    return window.pageYOffset || document.documentElement.scrollTop;
    }
});
</script>
<style>
  .tuan {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 999;
    background: #fffaeb !important;
}
</style>

Disable Ajax Loading if the code doesn't work. https://support.squarespace.com/hc/en-us/articles/115000253288-Ajax-loading

Q2. Seems fine here. Can you describe in detail?