Adjusting Work Visa to Add Freelance Work (Munich)

Hi everyone,

I already have my work visa and a full-time position here in Munich; however, I am interested in eventually doing some freelance work as an English Teacher/Tutor on the side and am looking for information on the process of adjusting my work visa to include this additional work. I have seen plenty of information online regarding initially applying for a freelance visa as a sole source of income, but haven't seen anything helpful pertaining to my situation. If anyone has any advice/experience with the process or could point me in the right direction, it would be appreciated.

Thanks!