Kurt, that can't be. Maybe you haven't got in touch with the right authorities.
There is -- by law -- a period of 120 years within that birth records are held non-public. But this is only for non-relatives!
If you can prove that he was your father (and you can, if you have a birth certificate that lists him), you are able to get the information.
So, the information about your father could (at least!) be at two sources:
1. Standesamt of the Munich authorities. Has entries back to 1876. Write them at least a mail -- if they are unable to do it, you have nothing lost. But I'm sure that they have the information and it is possible to get it. Contact is possible via https://www.muenchen.de/meta/kontakt.html
Or try to order the certificate(s) over the web (online), see https://www.muenchen.de/rathaus/Stadtverwaltung/Kreisverwaltungsreferat/Standesamt-und-Urkunden/Urkundenbestellservice.html
If you get through the online form, there is explicitely a possibility to get a birth certificate for one's father or grand parents!
2. (Catholic) church books of the diocese of Munich. Have information prior 1876, but may able to provide information also after that date. As a private person you can't look into the archives for yourself, but there are professional genealogists that can. See the information about family search at the diocese of Munich: https://www.erzbistum-muenchen.de/ordinariat/buero-des-kanzlers/cont/67273
You can use the google translator on the text, it does the job well.