I applied in-person. The process took 1 day. I interviewed at Universität Mainz (Mainz, Rhineland-Palatinate) in Aug 2019
Interview
The interview process depends on the recruiting professor. I presented my Master's research work and got genuine scientific questions from the group. I had the opportunity to interact with the professor and talk about the project that was offered.
First, I had an interview via Skype. Afterwards, my supervisor invited me to her group for another interview. I gave a talk there. In the end, she offered me the position.