thank you for addressing this question here in community.
AIf you have deportation ban according to §60 AufenthG you are not allowed to apply for family reunion(Familiennachzug)
In your case it iseven more difficult as it is not your wife, but girlfriend.
So in order to know your chances the best would be to get an appointment with the Ausländerbehörde and discuss with them the options.
I hope I could assist you in this, if more clearification is needed please feel free to reach out.