I have contact with the lady who works in the Jugendamt in Frankfurt am Main. Have not made contact in a while though. Every adoptee born in Germany is entitled to their adoption file, with all identifying information, once they are 18. You can have the Jugendamt search for family members. Or you can have someone poke around. If you want to chat further my email is Gabriele.Bornkessel.Harkey@gmail.com. Or contact the Meldeamt. Did you know your father is a dual citizen? I have helped quite a few German born adoptees find their papers and families. A lot can be done outside of the authorities, even in Germany.