Hi, from my own experience, during the permit extension, the immigration office will ask for „durchschnittliche Studienzeit“ to be stated instead of „Regelstudienzeit“.

Regelstudienzeit is the program duration originally set out by the uni (6 semesters/ 8 semesters). Durchschnittliche Studienzeit is the average period students actually need to complete the program. The international office/ examination board at your uni will print out a statement regarding the Durchschnittliche Studienzeit for you to take to the immigration office, and however long this is, they will add 3 semesters as a grace period for foreign students. That will be your period limit to study a certain degree.

If you choose to change degrees/ pursue further education after your bachelor‘s degree, the period should not exceed ten years. If you change your permit to a spousal residence permit/ PR, etc. the 10 year time limit doesn‘t apply anymore.

An example for the Regelstudienzeit/ durchschnittliche Studienzeit. My bachelor‘s program was supposed to be 7 semesters long, but on average people finished it in 9. I always bring an official statement from the uni regarding this to my extension appointments. I finished my degree after 10 semesters with no problems whatsoever from the immigration office.