Vastly updated the German translation

Lots of lines were wrong and contained typos. I checked every string I could find in the app and tried to translate it as accurate as possible.
Corrected a small error

A little mistake slipped through but was corrected, everything should be fine now
Furtherly cleaned up German translation

I noticed that I forgot to translate a small part (mostly the smart radio), corrected and improved some other lines too
Merge pull request #585 from Minty123/patch-1

Big update for German translation