In contrast to the Bachelor programm, in the Master the minor subject is optional and can be taken instead of the general studies. And contrary to the general studies, the grades of the minor do count towards the final grade.
The minor subject should allow students to continue their minor subject from their bachelor. As such there are currently only 3 possible standard minor subjects (12 ECTS): Mathematics, Economy and Electrical and Mechanical Engineering. To know which courses can be taken in the master, one has to look for the subject on this website.
In the masters program, the student has to participate in 12ECTS of general education or an optional minor subject. The goal of the general education is to broaden the horizon. As such no courses from computer science are allowed. On the positive sinde, the grades do not count towards the final grade, passing is enough (and normally pretty easy).
Non german speaking students do have to participate in a German language course, which counts as general education.