welcome in our community and thanks for your interesting question.
Unfortunately, before finishing your vocational training, there is only a very limited set of options left. In general, you could change to a work visa (if you find a job in an area where your academic knowledge or practical knowledge can be applied). At present, it is not possible to change to a residence permit acc. to 16f. residence act (i.e. just to join a language course). But the matter is more complex: If you intend to study on to get your Master’s degree and find a place in a master’s programme for which C1 is required, then the language course would count as part of your studies and it might be possible to obtain a study yisa acc. to § 18 a residence act (study).
If you want to work in your profession immediately without further studies, you could also try to further pursuit your professional training and learn German in your free time until you’re up to C1 and then find a job in your field of academic training, without endangering your stay here and without losing money and social insurance. There are very good online courses, f.e. at Deutsche Welle (https://www.dw.com/de/deutschkurse/s-2068) for free.
I hope my answers were useful for you.
If you have further questions, you can also join me at mbeon (www.mbeon.de).