run into another issue: when i change settings (language, continues) in the atomiswave-servicemenu and push "save & exit"
I mean, yeah. You've just made the nvram read-only, and now you're trying to save changes to it. That ain't gonna work. You'd have to do all that before you locked the file, while it was still writable.
Oops! Missed the part where you said it even happens without changing the permissions.