The earlier the better?
What age is best, who can give advice?
Yes I live in Germany but am neither Jewish nor Moslem.
But also many German Christians here do circumcision for medical and hygienical reasons.
Secondly its - as u stated- also for cultural reasons, as my woman is from Nigeria and wants it
to be done and I see no reason to oppose it, as long as it is done properly in hospital.
I see you are in Germany. Are you intending to stay there long-term?
If so, you should know that circumcision is quite rare in Europe. If you are doing it for some religious/cultural belief, ok, but if you think he needs to be done to 'fit in' with the other boys then you will be doing the wrong thing. It will make him unusual. In Europe, circumcision is only really done by Jews and Muslims.