Navbar that sometimes disappears

Hello everyone, can someone please tell me why when I open the navbar menu the header sometimes disappears, but if I scroll or I wait a few seconds it appears again. It may be a webflow issue?

Than there is this second issue, with the menu opened i still can scroll on page and i don’t want that.
I’ve tried every solution from the community but it doesn’t work for me.

Here is my public share link: [LINK](Webflow - SPACE)
(how to access public share link)