"This setting is managed by your administration" Windows Defender

righN said:

Nope, I used the Media Creation Tool. I did everything step-by-step as said in " 6. To do a repair install of Windows 10 with Media Creation Tool" on https://www.tenforums.com/tutorials/16397-repair-install-windows-10-place-upgrade.html

Sorry, too many assumptions from my side..
Sometimes it won't help (resetting permissions).

What kind of antivirus /antimalware do you use? Think we asked you about tweaking software and you said non, right?

righN said:

Had Malware-Bytes before but I deleted, so only Windows Defender at the moment. For tweaking software I have MSI Afterburner (just to check on temps and etc.) and Intel XTU to devolt my CPU a bit.

Ok, can you make another account (new user - also as admin) and test, if you can do it from there?

There is an utility, which can reset system permission. It is powerfull and be careful: Tweaking.com

Maybe it's time to ask: do you have system backups? Make system image, if anything goes wrong (Macrium free is excellent tool)

majorgeeks.com tweaking_com_windows_repair

righN said:

Do what? Repair? Devolt or run the .bat file for group policies?

Yes, run that file to enable you running Group policy editor. And check the post above again, I added something.

righN said:

Just tried, same thing happened. Going to try that tweaking.com tool now.

Just repair permissions (reset to default). If you have anything important (files) make system image.

righN said:

Well, it didn't solve my problem with "Some settings are managed by your organisation...". I think I'm just going to fully reinstall Windows.

guess it's the only thing you didn't try yet. Hope it'll behave then.