Welcome to the Wefugees Community and thank you for reaching out to us.
Regarding your question: Of course, you do not have to stay in your professional field after you completed the vocational training ("Ausbildung"). You may work in another area or even study in a completely different programme. For getting accepted by an University, you rather need to check the individual requirements of the respective programme.
I hope this answers your question and if not, or if you have any further questions, please do not hesitate to get back to us.
All the best,