flyingfkb

A few questions come up:
1) Did the grandfather ever lost his German citizenship, for example by taking on the South African?
2) If the grandfather did not loose his German citizenship did the OP have theoretically two citizenships for example by getting the German by "blood line" from his grandfather and his South African by "being born in South Africa"
3) If the OP had two citizenships, did he loose them both when taking the Namibian?

I think the questions is if the OP's grandfather lost his german citizenship. It does not matter if he renounce it actively or not. As soon as you take a second citizenship your German citizenship is gone. There are exceptions to this but you would need to apply for such an exception before you take on the new citizenship. For example if you are German living in the United States of America and you want to get the US citizenship without giving up you German you have to apply for an exception at the German embassy beforehand.

If the grand father for example took the South African citizenship he would automatically have lost his German citizenship. If this did happen before the OP was born he would not be able to become a German citizen and neither will his daughter. In case the grandfather never took on the South African citizenship and was always a German citizen the OP could argue that he gained the German citizen ship by "blood line". What I don't know how the South African citizenship is granted. Is it by "blood line" or also by "Being born in South Africa" like you get the US citizenship when you are born in the US. If you get automatically a citizenship just by being born in a certain country you will keep your German citizenship. So if the OP got his South African citizenship by "Being born" in South Africa and he grandfather still had his German citizenship the OP would have gained the German citizenship, too.

It get's even more complicated with the fact the OP took on the Namibian citizenship and renounced his South African. If for example he had a dual citizenship due to "being born in South Africa" and by "blood line" would the taking on of the Namibian citizenship automatically cancel his German?

So there are many facts to be validated before a final answer can be given if the OP's daughter can obtain a German citizenship or not.