Its done! After an almost three weeks long odyssey of trying four different drill machines with all sorts of different drill heads I finally managed to get all the wanted holes into my walls this morning!
Apparently my walls are made of super solid rock and only the forth of the drill machines could handle this situation. Thanks to everyone that took part in this odyssey by offering a drill machine.
And special thanks to Julie for offering the one that actually worked ;)
As a result of this I can finally have a house warming and show some first pictures of my room and the appartment …