Dear @Singh,
Welcome back to the Wefugees Community and thank you for sharing your question with us.
In general, the parents have to apply for the birth certificate (Geburtsurkunde) usually within one week after the child's birth at the registry office (Standesamt) which is responsible for the location/place of the birth. The parents are supposed to submit several documents, including their own birth certificates, the marriage certificate or if the parents are not married (if existing) the recognition of the fatherhood/declaration of the custody (Vaterschaftsanerkennung).
Please note that documents which are not in German need to be translated by sworn translators. Documents from certain countries are asked to get confirmed ("Apostille") from authorities in the country of issuing or legalised by the German embassy as well.
However, did I understand correctly that you are not in contact with your child's mother? Did you officially recognise the paternity? If not, this would be the first step. Otherwise the birth certificate will not name you as father.
I hope this helps and please don't hesitate to get back to us with any further questions.
All the best,
Meike