You usually don't need a separate confirmation of your citizenship to open an account with us. These steps are required:
Official ID document: This is needed for the Video-Ident or Postident process. You can legitimize yourself easily via video verification from home, or alternatively at a post office.
For non-German citizens: If you aren't a German citizen, you also need to provide a registration certificate. This also applies if you're a German citizen living in Germany but are identifying yourself with a passport.
If you have any questions, you can always contact [email protected].