Work Permit for China

Dear,
I am a luxembourgish citizen and I was hired by a german company for their offices in Shanghai.
Do I have to do my visa application through the embassy in Dommeldange or do I have to go through an agency?
Do I have to do the application in Luxembourg or Germany?
Could you also tell me which documents i will need and how long the process will take more or less?

Thank you.
Best regards