Changes to "home" show only in my own browser

Hi,

1. I have been experiencing issues, when accessing the "home" page in the backend. It takes ages until I can do anything. And then I have to wait for every single input. It took me half an hour to change three sentences. This occurs non-stop for weeks now. But only on the "home" page. Other than the usual updates I hadn't done anything to the page to cause this. Other pages are slow as well, but not quite as bad.
2. The adjustments to the "home" page through the customizer (I had to edit the menu) only show in whatever browser I log into the backend of my site.
3. The pages built with the wp bakery builder are the ones being extremely slow in the backend. Pages built without are easily accessible. As are articles (but I dont write them using the bakery builder).

• I cleared the site cache
• I cleared the browser cache
• I have a 250/50 internetconnection (not using wireless lan)
• Plugins are all up to date
• I even created a new menu, but that didn't change that
• I accessed 6 browser to check over three devices - same problem

What I need asap: is a fix to the menu problem. Because due to revolution slider changes one page (that only used revolution slider) was completely messed up. So I wanted the easy fix - take it out of the menu.

Didn't work.

Took that subpage offline, but that isn't really a fix.

Website: www.rockyourstudium.de

As I am about to modify the whole page I need to be able to work on it and not only write new articles.

Thanks in advance

Patricia