Before applying for a German passport, it must be resolved which surname you bear with regard to German law. If you have a German birth certificate, the surname is usually determined. If you only have a foreign birth certificate, the name entered therein is not always acknowledged under German law.
It is possible that, according to the German law, no surname is stipulated and must first be declared. It may also be, that a surname is fixed under German law, but does not match the name entered on the foreign birth certificate. Then, under certain circumstances, a name change may be possible under German law. This also requires a separate declaration
You will find information on common constellations below.