It took four months from first skype-interview to full day interview in Leipzig. Total ignore to my email and skype messages during this time. But they talked with HR-agent. In day of personal interview they asked many private questions I don't really wanted to answer (ex.: about my girlfriend, about her work).
Test task not so hard but pretty big for given time (less than 6 hrs). You must guess what they expect from you: 100% of features completed or following best practices. You can try to clarify expectations about the result if you lucky enough to find CTO (Stefan) but I could not. In conclusion I got no chance to talk with CTO after finishing the task. So expectations might not be satisfied and no chance to explain why. After this day, total ignore again. Two weeks later HR tells my about rejection with "technical" reason. My attempts to get this info (via email, skype, whatsapp) met with complete silence. Avoid.