You can find an overview of all courses offered in each semester in the LSF-Portal (not fully translated, but you can find an overview of courses held in English here) . You will receive your login after enrolling, but you can also access the current course catalog under Lectures without logging in.
You can put together your own schedule by looking up the dates of the lectures planned in the module handbook (Bachelor/Master) for your semester in the LSF. Start dates of the courses are also published in the LSF and on the websites of the teaching areas with sufficient time before lectures start. You will also receive information and help on creating a schedule during the orientation phase (O-Phase).
Lectures do not require registration. If exercises and tutorials ask for registrations, this will be clearly stated in the corresponding lecture. Only seminars are subject to a separate registration procedure.