Thank you for reaching out to the Wefugees community!
Unfortunately, I am not familiar with the Austrian education and trainee system. Referring to Germany, providing a certificate to prove your German skills would probably not be essential. As long as you can convince your potential employer, that you understand and speak the language on a sufficient level. Especially, if it comes to your performance at school.
However, I assume that you need to provide certificates of your general school degree.
In any case, I would recommend you to consult an education and job adviser to discuss your opportunities. Please let us know, if you need support in finding one close to your place of stay.
All the best,
P.S.: A similar topic was discussed on this platform earlier - you may want to check this thread.