Elective modules have to be registered at the examination office.
The online registration should be possible for compulsory and compulsory elective modules. The online registration for your second repeat examination is not possible. You have to register theese at the examination office.
Please note that an online registration is only possible during the specified registration periods. Registrations after the deadline are only possible with the written consent of the examiner.
In the Gastsicht  you can select your degree program with the correct examination regulations and you will get an overview. There you can also see whether the examination has been approved for online registration and which registration deadlines have been set.