Unfortunately i haven't found anything useful on the net how to accomplish something like that. I would guess it could be possible with a custom rom? But given the phone isn't very popular i can't find much on that either and i'm not very knowledgable about stuff like that (i can barely manage to root a phone).
Hope someone has a idea and can help us out or confirm if there is no way to accomplish adding a language to the phone. Thanks alot!