Welcome to the Wefugees Community and thank you for reaching out to us.
On your first question, I really don't think that a non-EU citizen could not work in a German bank after finishing the respective vocational training ("Ausbildung") in Germany.
Regarding the visa, I can unfortunately not share any experience or reliable information. But you are right, Germany is short of staff in certain industries and I assume that the visa procedure might be easier for applicants for these high-demand occupations. I will link my dear colleagues @mbeon-Christine and @mbeon-ruth here. Maybe they can add some more details and give an advice.
I also recommend you to check the "Make it in Germany" website, where you find more details on the requirements for the visa and the procedure in general.
In any case, please don't hesitate to get back to us with any further questions.
All the best,