Let us know if he finds the message and replies. Our mirror image forum is 'The Fly Forums UK & Ireland' there are members there who may be very familiar with Germany and I know some German members as well. Here's the link; Fly Fishing Forums. Fly fishing news, chat, reviews, advice and reports. Join over 50,000 registered members.
You will have to register as you did here and then find your way around a bit. The forums are powered by the same software so it'll be easy to find the proper sub forum to post your questions in.