same with me... I just signed up 24 hours ago and got into this bad gateway thing right after getting access to the ccc. I am still struggling with the ccc, It's not a really customer friendly UX. well I don't know, if I should stay at netcup. I have problems with the let's encrypt SSL - and all I have done so far is installing Wordpress???
I feel your frustration. Had the same when I joined last week-end. It's going better as it now runs smoothly. (And I'm amazed by the product that Netcup offers.)
Good luck