Welcome to our site and thanks for your question. My name isXXXXX and I will do whatever I can to try to tell you how to get the certificates you want.
The information you seek is not online. No Germany information after about 1912 is available online.
German law only allows birth certificates to be be issued to someone named on the certificate (i.e. the child, or its father or mother), or a direct descendant. Descendancy must be proved with the birth certificates of the later generations. Since you know your date of birth, you can obtain your own birth certificate from the Standesamt (Civil Registry Office) in Hamburg.
You can get your father's from the Standesamt in Hannover. In the event of a name change, the name on the certificate is probably the new name and the parents' names would be those of the adoptive parents. He would have to hire an attorney to petition the court to have the adoption records unsealed to learn the names of the birth parents. Of course none of this is available online and no one can obtain the birth certificate for you online.
An alternate method is to give your representative your power of attorney and the requisite proofs and have that representative work on your behalf. However, the information is not online and either you or your representative would need to go through the proper legal channels to obtain the requested documents.
Here is the contact information for the Standesamt in Hamburg. It is best to contact them by letter, telephone or email for further instructions:
DISTRICT OFFICE NORTH HAMBURG - CIVIL REGISTRAR GENERAL AND REGISTER
Phone: +49 40NNN-NN-NNNNFax +49 40NNN-NN-NNNN
For Hannover, here is the contact information:
Tel.: 0511-168 4 29 58
Fax.: 0511-168 4 33 76
It isn't difficult to actually get the birth certificate from Germany, but it is something you will need to do on your own or hire one of the many companies that specialize in representing people attempting to obtain legal papers.