Documents wise, we included everything that we read on the internet that might be helpful, as we were applying for a 90-day visa and were trying our best to maximize our chances of getting it. We included: application form (filled in on the Visa Application Service Centre in Berlin website and printed), passport copies, copies of pages with Chinese visas in previous passports, Aufenthaltstitel, copy of Aufenthaltstitel, 1 passport photo each, detailed day-to-day itinerary for 90 days, return flight bookings from Germany to Beijing (fully refundable), hotel bookings for every single night (also fully refundable), a letter of invitation from a friend in China, and a copy of the friend's Chinese ID card.
For the letter of invitation, we used the form provided at https://www.visaforchina.org/CBR_EN/gen ... 5197.shtml
We heard from a travel agent in Berlin that it should also be possible to receive a 90-day visa without the letter of invitation, but we wanted to be extra safe.
Once the package arrived at the Visa Application Service Centre in Berlin, we received an email with payment information. This included the embassy fee, Service Centre fee, and postage handling fee. After we paid, we didn't hear anything more from the Service Centre, and the online application status check didn't work either. However, after only 5 days, our contact received our passports (with visas for 90 days) back in the post!!
So we can confirm that applying for a 90-day visa in Berlin by post works
