Apparently, everyone here has an opinion as to whether or not making music and teaching at home is legal or not. As far as giving further advice from my 10 years of living and working here as a professional musician and teacher, I am going to suggest that the OP join the SMPV (costs 145 per year) and get a free Rechtsberatung (legal consultation) available to all members. They will surely be able to clear up any doubts or worries you may have, and you can rest assured that they are on your side.

But I repeat, no one and I mean no one can forbid you from making music in your home unless you yourself were to sign a contract to that effect.