Menu hidden behind sticky header

Hi!

Page is mysteryrooms.pl Password is “pokojetajemnicze”.

As You can see, menu is visible only, when header is transparent. I couldn’t fix it with z-index.

Menu also doesn’t work but i hop it will, when i solve visibility problem.

https://ww.wp.xz.cn/plugin/responsive-menu

https://ww.wp.xz.cn/plugins/responsive-menu/