It is not possible to change to a language study visa (paragraph 16f of the residency law) from a student visa without finishing your studies. It is only possible if you complete your studies.
You can, however, change to a visa for an Ausbildung without finishing your studies. I advise you to use the time you have to work on your German as much as possible in order to help you find an Ausbildung.
You write about needing to attain B2 level of German for an Ausbildung. Is there a specific type of Ausbildung or company you are hoping to find which have told you B2 is required? While it will of course help you with an Ausbildung the more German you know, there is not a standard legal requirement for any specific level of German to do an Ausbildung. It depends on each particular company or vocational school which level they require. It could be that someone speaks German very well but that their written German isn’t yet so good; such a person can also do an Ausbildung. And you can also learn German alongside an Ausbildung. For example, in Leipzig where I work, there are special part-time evening German course especially for people doing an Ausbildung. I wish you the best of luck!