Also, put a note in the envelope and write down your Chinese address. When they reply, just stick a sticker directly, which is convenient for everyone (this is very effective).
The next step is to send a letter, and then take it to the post office, so that they can speak more clearly. Otherwise, there are not enough stamps, the postmarks are all stamped, and it is not a loss to return the letter. General stamps 6-7 yuan, envelope stationery stores are sold. International envelope 1 yuan.
The following is the address of Bayern. Good luck!
file control block
Autograph
PO Box 90 04 5 1
D-8 1504 Munich