Generally, you have to be registered for a course in order to participate.
However, to give you the opportunity to try out a sport you are not familiar with or to get to know a (new) instructor, there is a so-called "taster week".
The taster week takes place at the beginning of each summer or winter semester programme. During this first week of the lecture period, you can take part in most courses without being registered for the course. Whether a sport is part of the taster week or whether the sport is excluded from the taster week for safety or sport-specific reasons is indicated under the description of the respective sport. If a course does not start until after the taster week, it is not possible to have a taster session in this course. Because many courses are already fully booked after the taster week, there is always a further booking start on the Monday after the taster week, where spots held back until then are released once again for the courses that were part of the taster week.
There is no taster week in the two holiday programme periods.