Various software and Apple-ID issues after installing macOS Sonoma using OCLP on MBP (2016)

I installed macOS Sonoma using OCLP on a 2016 MBP. There were no issues in the process. However, I have the following problems

• I can’t use any Apple-ID (tried two) to log into iCloud or the AppStore.
• Downloads from Safari cause Safari to freeze.
• Different windows (Finder, Firefox) become unresponsive and somehow seem deactivated, while the dock is in the foreground. This can only be resolved by force quitting the app or rebooting.

Do you have any hints how to proceed from here? I don’t want to ditch this fine piece of hardware.

Thank you