This unwillingness to discuss private time with colleagues reveals both the German distaste for small talk, but also the German desire for privacy.
Germans have a clear and robust sense of what should be in the public domain and what should not, and although there are exceptions for good friends, finding out what your colleagues get up to outside of work requires military grade interrogation techniques.
With waterboarding out of the question, I am left with little recourse other than to linguistically trap colleagues into giving away small details of their lives. The excruciating process of trial and error can last for years, until one day a colleague feels comfortable enough to actually tell you directly what they get up to when not at work.