(A)is Brazilian married to (B) german citizen
(A)have been in Germany for 5 years, applied for a student visa and then
married to german national in 2016 which granted me a residence permit for 3 years until april 2020
we have lived together until November 2018 where the separation year started and now
after switching our tax class to 1, we only share the health insurance and no date for divorce yet.

during this period (A) have worked for 2 years, got a b1 language certificate and currently registered in german school as a visitor student

what are the options for (A) and could convert his visa to studying ?

Please Help !