How to make "menu" and "stop playing video" in JS?

Question

JavaScript

Good, gentlemen!

Please, tell me how it is possible to implement on this

site: 1.) Menu, 3 links to sections, on click closes the page where the user is located and opens the desired one, this is 1 html document, I think it can be solved using ID's and tracking the click of a cross , it is possible on Jquery.
2.) So that when you turn on the video and close the tab, the video stops (I read that you need to add autoplay and when you close the tab, remove autoplay and add something else - but not the fact that it will work).

I think it's not difficult to do this (probably), the logic is clear, but since I'm only learning JS, for me it's a bit complicated. :(

Thank you very much in advance for your help!