welcome to the Wefugees community and thank you for sharing your question with us.
According to the procedure references of the immigration authority Berlin, changing the purpose of your stay is possible in case you submit a contract for an apprenticeship and prove that you won't be able to finish your studies despite all your efforts. Nonetheless, the decision whether you will be given a residence permit for professional training is at the discretion of the immigration office. The period between applying to the Studienkollegs and the start of the apprenticeship should not exceed three months in general. And you should choose an apprenticeship in a so called bottleneck profession. A list of the professions can be found here: https://www.mangelberufe.de/facharbeiter/.
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 consultancy for migrants via the mbeon-app, which you can install on your smartphone for free. Download it via App Store or Google Play Store. 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. Further information: www.mbeon.de. Best regards mbeon-Christine