To change subject or university, you must first clarify everything in detail with the university you wish to change to. The best time to do this is in June for the following winter semester and December for the following summer semester. You should clarify the following points:
Which courses are offered when, structure of the semester
Admission restrictions, enrolment
University entrance qualification
Transferring credits
Study costs, accommodation
Please note: Changing university during a Bachelor’s degree is often very difficult.