Is it neccessary to make an appointment for a China visa application in person?

There is no need to make an appointment for a China visa application in person.

Thank you. After submitting the written application would the embassy post the passport back to another German address . As I understand that may take up to 4 days is that correct?

The mail back service is not available at the China embassy in Germany. After 4 working days, you need to go to the embassy to pick up visa, if you can't come to the embassy in person, you can ask someone else to pick up your visa and passport by giving the pick-up receipt to him/her.