Re: Edge again
Are you trying to change the language for Edge alone?
It's my understanding, at least for the stable version of Edge, that it should follow whatever language you have set as the Windows Display Language under Settings, Time & Language, Language Pane. I don't know if any of the preview channels (Beta, Dev, Canary) do this, though I'd expect they would.
If you have the stable version of Edge installed, and all your other system utilities like File Explorer, Settings themselves, etc., all show up in Czech then I'd report the issue to Microsoft via the Feedback Hub or from within Edge itself via the Send Feedback button (if it exists in the stable version. I can reach it in Dev by hitting ALT then left arrowing until I land on it.)
Brian - Windows 10 Pro, 64-Bit, Version 1909, Build 18363
Power is being told you're not loved and not being destroyed by it.