thanks for reaching out to the Wefugees community and for sharing your question.
After 49 months in Germany you will receive a general work permit which doesn't involve the employment agency any longer. This gives you more options when you're looking for a better job, e.g. But you still need the approval of the immigration authority, that is your work permit is linked to the period of validitiy of your temporary resident permit.
I hope my answers were useful for you and I'll be very pleased if you contact me again with further questions. I'm a member of the mbeon-staff and I‘ll be glad to guide over a longer period of time. mbeon is an online advisory service for migrants via the mbeon-app, which you can download on your smartphone for free. You'll find me in the mbeon-app under my name „München, Frau Müller“ and get confidential one-to-one advice in a safe virtual room where nobody can read messages. For further information please visit www.mbeon.de.
Download for Android: https://play.google.com/store/apps/details?id=de.zone35.mbeon
Download for iOS: https://apps.apple.com/de/app/mbeon-messengerberatung/id1408795643