Not in Germany, but fairly close to Dresden -
DSA in Hradec Kralove, Czech Republic. They are very businesslike, honest and relatively inexpensive. Unlike most other schools, they charge you for the flight time from takeoff to landing, not from startup to shutdown, and don't impose any extra fees for ATC, instructors, etc.
One important thing to keep in mind - they don't give full-fledged theory lectures; you are supposed to read the books first, then come for consultations. Depending on your preferred mode of learning, this may be an advantage or a shortcoming.