There is usually a registration phase between completing the Bachelor's degree programme and starting as an enrolled Master's student, during which you can apply for modules with limited participation. Technically, however, you can only register yourself once you have been transferred, i.e. at the start of the next semester at the earliest. As a gesture of goodwill, the Office of Student Affairs offers students in this situation the opportunity to register manually for up to 20 ECTS in modules with limited attendance in the first phase so that they have a chance of admission.
In addition to the desired maximum of 20 ECTS in modules, please send a news overview (screenshots are sufficient), which shows that you will certainly be studying in the Master's programme in the next semester. If the evaluation of the last achievements is still pending, a confirmation from the professorship that the achievement has been passed is required.
It is not possible to increase this scope or to register for modules that are not limited.