Train a German Model in Flowtron

Hallo,
i am going to train a model with a german speaking language sets.
I read a lot of documentation and the training with english datasets work for me.

But i want to train a Model in my native language and the results were not understandable.
The output is either english nore german. i used a librivox de dataset.
Is it possible to get a kind of instructions how i can realize this?
What to do, Symbols, Cmudict. etc.?

thank you so much,

Kind regards,

Steffen Wünscher