[2019] Server Error Sign-in Timeout

Please run through the solutions for this particular error listed here.

It sounds like you may be accidentally playing on the ‘Modded’, as opposed to the ‘Official’ realm. Your realm can be changed using the checkboxes above the ‘Play’ button within the launcher.

If that isn’t the case, please restart your PC.

It’s almost always a local issue, for most people a simple DNS Flush can sort it out. In this case it could be an ISP-related hiccup perhaps, considering you’re both based in Germany - I can’t be sure.