Dear @Pan123, 
thank you for your question and congrats for the happy occassion. 
as for your question: 
- the time it might take depends on the authorities in Kenya, however you could get a certification by the embassy of Kenya in Germany, that proves that your divorce documents are not fake. 
- as for the birth certificate, if you have a Auszug aus dem Geburtenregister from the Standesamt, almost all German authorities accept it on behalf of the birth certificate. 
https://service.berlin.de/dienstleistung/318960/
If you have further questions, please do not hesitate to reach out to us. 
Best regards, 
Nilab