Schlager are very popular here.

Language barrier is the main reason, I believe... but regarding industry, brands, sports and culinary, there are a lot of things from Germany that are popular around the world.

LOL... is that so? I know a few people who traveled to Germany, they said exactly the opposite to me !

World War 1 and 2 pretty much spoiled any chances of people liking German culture. Also, Germany hasn't really tried to go their own way or be a trend setter in a long time. I like the beer events and the dresses the girls wear for those things. The music is meh. They just copy the rest of Europe for the most part.

What you talking about, there are nazis in every other game and a hell of a lot of books and movies about them.

Is there anything more popular than the nazis that they are know for.

The language definitely is one of the reasons. Most stuff can't even be translated properly without losing content. Porting stuff into German however is something people are capable of.
Also, German "pop culture" is mostly just copying what's popular anyways. There's a great movie/story? Add 1-2 years and the Germans will come up with the same thing but less production cost resulting in a poor imitation.
If it's not a poor imitation, it's still just copied.
Most stuff is copied ("imported") from the US and you could argue it's just to have a good image so nobody's pointing at that World War thing again because some German had their own thoughts put into a song/movie/book.

The few things that aren't copied don't make it outside of the country because they are simply too German. Songs in German are probably niche due to the language and how it sounds. There may be the odd thing like Rammstein but, surely, most people listen to it because it's how they think German sounds like when in fact they just overuse a stylistic device and put it on mainstream rock.
Movies are packed with jokes that other countries don't understand and their voice acting isn't as established as the German one, Germans have had to translate everything forever and became pretty good at it (incl. translating puns or making up their own situational jokes), thus German dubbed movies are accepted whereas other countries prefer the original English version of movies due to the lackluster voice acting of their native language.

Before German pop culture can get anywhere other countries would have to take a look beyond Bavaria. As long as "Germany" is all about the Alps, wheat beer, yodeling and lederhosen there's no way actual German pop culture would even be labeled as German.

I think it's because of your interest.

Media such as movies and music are dominated by the English culture.
Things like cartoons, comics and videogames have had a big influence from Japan.

What about Spanish? You think it is less popular worldwide than Japanese?

Try harder.
You need to push outwards.

Ramstein, Boney M, Djinjis Khan.

Germany does have some stuff.

^ Plus this: