Sticky bar not solid on some parts, other parts are fine

Hi everyone!
I am creating a website and my nav bar is acting out! :wink: It’s supposed to be sticky and solid yellow, but: on some parts it shows the text below through, on others it’s how I want it and on one page it shows the content over the bar?! I can’t find the mistake, maybe someone has had that happen before. I would highly appreciate any tips.

Here is the read only link:

Many thanks in advance from Vienna :slight_smile: