Sorry - but this is a stupid sentence. Only becasue Nelson Müller has a black skin thid not means he is not a German or a second kind German with "foreign" roots. Nelson Müller is a typical German. 100% Gernan.
Let me explain to you: The word "German" not exists in "Germany" - where also this word not exists. Wir selbst sind keine Germanen in Germanien. A German is a German only from outside of Germany. In very most cases we Germans are a mix of Gemanics, Celts and Romans (including Jews). So Nelson Müller's ancestors are perhaps from the Nubian Legion - or not. I will ask him when I will meet him - or not. I guess "or not" because it could be we could speak about something else - or not.
Not your problem, stranger, who not lives in Germany and never will become a Gernan.
I remember in this context and older lady in TV who came once fromTurkey. She said:
"When I came to Germany I knew everything about Germany. Now I live more than 40 years here and I do not really know Germany."
More German never anyone will be able to be.