Gidzzz here's the updated German translation you asked for.
Added the new strings and they're also some small tweaks.

[Edit:]I see NightShift79 also posted a German translation. Better two than none. "Doppelt hält besser", as we say here in Germany

Some remarks to my translation:
-I tried to match the translation of the original Media Player as much as possible.
-The translation is now complete (except some possible errors) and I even translated terms like "Lyrics", "Album Art" and "Now Playing". Not everybody likes this kind of translation as the German terms for this are IMHO not very precise and self-explanatory.
-German phrases are often much longer than the English ones. ATM some translated strings are too long for some fields. The original player therefore sometimes changes the font size. Is this possible with QT Linguist?

[Edit2:]

I found a strange translation bug:



Looks like some kind of problem with German umlauts. But my translated text string is "Frequenz einstellen" not "Frequenz auswählen" as the screenshoot shows. Any clue what went wrong here?