Problem in the menu?

This the website I am building and if you open the menu, the navigation part of menu scrolls down. It happens only on the pages that has the Video mask section because it has the height of 300vh. The navigation part of menu the menu takes that height. What should we do to prevent it?

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

The Home page at desktop breakpoint showing the menu icon and the video mask >>

After I click the menu icon >>

Seems all fine here except for a missing element (the little ? mark)