German Chatbot or conversational AI
To start with chatbot first of all you to decide which type of chatbot are you trying to build.


Order placing bot
Chitchat bot


Both required different approach to solve the problem.

Order Placing Bot required multiple model for different task like intent identification, named entity recognition, state machine.

Chitchat bot required only 2 person conversation dataset which is available easily on kaggle.com

But if you are looking for specific language dataset then it difficult to find it in both type of bots. For that either you use any translation api which you to pay for it or use web scrapping techniques to do same task at free of cost.