Dimension Start window is frozen

Hello all,
my problem is the following:
The application opens and the start window appears with the suggested tutorials and the buttons "Open" and "Create new". However, I cannot click on anything nor can I scroll in the window,  or even close the window.

I have already uninstalled and reinstalled everything with the Cleaner and increased my RAM to 48 GB. The application does not work in safe mode on the Mac either.