Windows 10: Start menu, settings, store and all apps not working Windows 10 20h2

Good morning

Some days ago, I had problems with Windows Update, but I could not do an in-place upgrade because of the 20h2 bug, so I decided to use the program here: Repair Install Windows 10 with an In-place Upgrade

The process ended successfully, and I have been able to keep my files and upgrade.

When everything ended up successfully, I tried to open Microsoft Store, but it crashed every time.
So I tried the troubleshooting inside the Settings, that found the problem but didn't solve it.
When I have used the powershell command Code:

it showed many errors.

When I restarted:

• Start does not open
• Microsoft Store and all the apps (built-in included), when opened, show the popup error "explorer.exe class not registered"
• I cannot use win+x or win+i
• Settings do not open up
• Only .exe apps work well (no errors)

So I have tried to:

1. sfc and dism (also from safe boot) --> No errors and repair successful
2. Do the powershell command again
3. Create new users
4. In place upgrade two times

But no one of these methods worked.

Currently I am using build 19042.685.

I don't have antivirus or optimisation programs installed.

Is there a way to solve this problem without having to format all the partitions?

Thanks in advance for the help!
W.

:)