Hi
Max
The left hand side is the HTML and the right hand side is the CSS, you can click on the various div’s on the left and the CSS that corresponds shows in the right.
If you view your site, the black menu on the right hand of the screen has now gone ??
Maybe this is a Caching issue?
After you do the changes, make sure that you clear the cache and “hard” refresh the page in your browser to be able to see the changes right away. If you’re not sure how to “hard” refresh a page in the specific browser you’re using, just Google it and you’ll find instructions how to do that. Also, don’t forget if you have any Caching WordPress plugins installed, or use a CDN (like CloudFlare) to also either clear their cache or disabled them for the time being altogether. This site has some great instructions on cache clearing: https://www.wikihow.com/Clear-Your-Browser%27s-Cache
Cheers