You are German, thus you have the unique opportunity to read the German literature on this topic, e.g. the big tomes of Günther which are written in Fraktur. The total spectrum discussed in these is huge, but it's very interesting to say the least. Of course it doesn't contain the newest scientific discoveries as of today, but most of it holds up pretty well. While reading it, don't fall into a sort of mania though. Houston Stewart Chamberlain is also intersting.
Only a few Germans are and were pure Nordic (and/or Phalian). Germans, like most Central Europeans are a mix of the 5 Europid main races. In the case of Germans, they are about 50% of Nordic blood, the rest ist Dinaric, Mediterranean, Alpine or East Baltic and a bit Sudetic. But 50% doesn't mean that 50% are blonde and blue eyed. There are only maybe 5% left and this is declining for years now.
Because the darker colors of the other white races are always dominant in heredity, we could have a Nordic man before us who expresses all the Nordic physical characteristics but has dark hair. Or someone who looks Nordic but behaves typically Mediterranean (body language, etc.) because of his inner life (racial soul). In almost the same manner, there could be people who don't look very Nordic but express the Nordic archetype in their daily lifes.
In summary, every German has Nordic blood, but with admixture of the other white main races.
But this is all secondary. The most important fact is the racial soul, the character, which in the case of Germans is Nordic. Especially the Germans went through a centuries-long special (natural) selection of the 5 main races. The ratio of the mixing by selection gave them special capabilities of a broad kind, a special gene pool with predominantly the best abilities of all, if you will.
This holds true for the other "real" Europid peoples in Central Europe too, though the Germans expressed it in the most memorable way.
Look at photos of Hitler in WW1, he is Nordic-Dinaric, maybe a bit Phalian. The Dinaric characteristics you can see especially well when he was younger (like the WW1 photos). Or look at the genius of Richard Wagner, who was Nordic-Dinaric. He wouldn't have been as great if he was only Nordic or only Dinaric.
The most important task today is the survival of the white race as a whole. And after that we need to start maintaining our gene pool with the right amount of admixture.
TL;DR: It's not about the looks but the aspect of the racial soul.