Windows 10 Pro display different languages when right clicking on the taskbar

It's most likely have to do with an update from MS in early February.

I have visited swedish forums where lots of people have the same problem !

All we can do is to wait for MS to fix it !

Is there a System Restore point, this is more effective as a way to go back before the date and time when the problem returned?

System Restore is your first line of defense if Windows ever malfunctions as it can run even from recovery media to get you back before a problem started like a time machine. It should always be turned on C drive with plenty of disk space (5-15%) configured. Here's how to check and when necessary how to run System Restore: https://www.windowscentral.com/how-use-system-restore-windows-10

Then I'd pre-install Hide Updates tool so you can quickly run it to catch and block the suspect Updates, wait a month to try again or until the next Feature Update when they'll be rolled in and usually don't cause the problem again:

Hide or Show Windows Updates in Windows 10 | Tutorials

You seem to have exhausted most if not all reasonable avenues to fix the issue, in vain unfortunately. My language doesn't seem to have been as affected as yours, but then again there might be a lot of untranslated strings that are just not in as visible areas of the OS interface as the examples for Swedish.

In a different thread another user confirmed the same issue with Portuguese (Portugal) across multiple devices, but said that switching to Portuguese (Brazil) didn't appear to have the same issue. I honestly don't remember something like this ever happening... in any case, I have yet to submit my own report through the Hub. I hope this gets fixed soon, although the lack of visibility and severity might not help putting pressure over MS to tackle this in a timely manner.

Hi there ner00

I just reported it with the Microsoft Feedback Hub app.

You seemed to have found the culprit but as you said it's now up to Microsoft to fix it !