Using New Outlook on Windows for professional communication and productivity
I have found a second workaround:
to delete all email accounts and old informations in the new outlook, I deleted the folder
C:\Users*username*\AppData\Local\Microsoft\Olk
After I started the old Outlook once and switched from there to the new one. that way, I got a clean new outlook and could reconnect my accounts again and the settingspage is back too