How should you know which courses to attend and when? There are subjects, such as medicine, in which the course schedule is already partially or completely set in advance. In other degree programs, you are on your own when it comes to scheduling.
Bachelor's, master's, teacher education modularized: Annex 2 contains everything you need
In bachelor's and master's degree programs, scheduling is usually not a problem. In the Examination and Study Regulations that regulate your subject, it's the so-called Annex 2 that specifies the exact achievements you are required to evidence in order to successfully complete your degree program. The same Annex 2 also stipulates which courses or modules you must (or at least should) attend in which semester. The Examination and Study Regulations, including Annex 2, can be found online under the respective degree program's description. You can find out when and where the courses you need to take are offered in the University Catalog. The University Catalog is available online via the LSF online university catalog.
Here you will find the courses / classes listed in terms of course content, academic literature, performance requirements, and target group.
Should you struggle to follow the Examination and Study Regulations — don't despair yet! The introductory courses for your subject(s) will also cover exactly which courses you absolutely must attend and how to register for them. In addition, if you miss this / these introductory course(s) for an important reason, academic counseling (at faculty level) can also provide you with information.