Lovely Story! I enjoy the use English with the little bit of German and French thrown in. Love the characters as well.
A wonderful story, but I've found the sporadic use of German phrases detracted from the experience. Why is any given dialogue in English or in German? There was no discernible pattern. Were the characters themselves bilingual? That seems out of place given the setting.
I also noticed it, since the implication of the setting is that the characters are speaking German, and the story teller is translating. I think it's just a bit of artistic license.