Changing a door handle is easy. Most doors in germany use a simple screw or a pin to fix the handle. Just loosen the screw or push out the pin (e. g. with a small nail from the underside) and removing the handle “should” be easy.
When I tried to remove the handle of our bathroom door it didn´t work. I removed the screws but the handles did not move an inch.
Being frustrated I tried to get the things off using a hammer. …that didn´t work either. Since the last visible screws were the ones fixing the face plate I decided to remove them. After that removing the door handle was easy!
The handle was secured on the inside (of the face plate) !