Dark screen when navigation bar - dropdown opened

Hi everyone,

I made dark screen when the nav bar drop down is opened. My general issue is that when you interactive thru the dropdowns it looks like the screen flashes. That effect is because i set the div (named: ‘dark-opacity’) on 0% opacity when the dropdown is closed. How to make dark screen fixed while interactive thru the dropdowns?

Here is my read only link:

Here is the link of page how it should look like:

Here is my public share link: LINK
(how to access public share link)