NEED HELP! Body scrolls, when drop down cart menu is open


I’m having a seriously hard time trying to prevent the body of the page from scrolling when the drop down cart menu is open - I’ve tried what seems to feel like hundreds of workarounds, but I Cant figure it out.

Any help would be really appreciated

Warning: The site is really messy - I’m no expert.

Here is my site Read-Only: LINK
(how to share your site Read-Only link)