Registration for the courses is done via Stud.IP. The registration periods will be announced in good time via the mailing list and on the websites of the course.
The seminars are usually designed for a certain number of participants. Therefore, you should register in time for the start of the registration period in order to get a place in your desired seminars.
As a rule, there is no limit for the lectures. Nevertheless, you should register for the lectures on Stud.IP to get access to the lecture notes and not miss any important information.