By Sam Wilson
BBC News, Dortmund
Mr Yildirim says Turkish nationalism in Germany is "positive"
Hakan Yildirim says he is fully behind Germany in the World Cup. If Turkey were in the competition, however, it would be a different story.
In the Nordmarkt area of Dortmund, a quarter with many Turkish families, Mr Yildirim, 20, helps run his father's restaurant, the Saray grill.
There are many German flags hanging from balconies and lampposts, and protruding from car windows.
"We support Germany, of course. We live here, we eat their bread!" says Mr Yildirim. "Our families are here and our future is here."
In other Turkish areas it is no different. There were reports of celebratory gunshots over Berlin's Turkish neighbourhood of Kreuzberg after Germany's victory over Ecuador.
Turks make up the largest ethnic minority in Germany, but there are none in Germany's World Cup squad. It is not as if the squad is not diverse - almost a quarter of the players have some foreign blood.
Miroslav Klose and Lukas Podolski are ethnic Poles, while David Odonkor and Gerald Asamoah have parents from Ghana.
This is not an accident of timing - there have been very few Turks to play for Germany. One great player, Mehmet Scholl, was a notable exception.
The future looks no different.
One of Germany's most exciting young players hails from Borussia Dortmund. Nuri Sahin became the youngest player ever to feature in the German Bundesliga in August last year, at 16 years old.
But despite approaches from the German side, he has opted to play international football for Turkey.
German-born Nuri Sahin, a rising star, has opted to play for Turkey
He made his Turkey debut in October - against Germany - in a friendly. He came on as a substitute with four minutes left - and took only three to score the winning goal.
"I was actually born in Germany but feel more Turkish," said Sahin, explaining his career decision.
"I learnt my football in Germany but as a Turk, I have never thought of playing for Germany... Scoring a goal in my first game was nice but it is even better to score against Germany."
Turkish areas of Germany are often said to be parallel societies.
"They feel German in some sense, but they are not fully accepted citizens," says Dr Dirk Halm, a sociologist at the Centre for Turkish Studies at the University of Duisburg-Essen.
He speaks about a "double identity" among second- and third-generation Turkish immigrants.
He is not surprised that most seem to be supporting Germany, but says if Turkey were playing in the World Cup, "we'd have a very different picture".
Turkish communities fly German flags to show their support
This is not surprising, he says, as Germany has not gone out of its way to include Turks.
He refers to the "anachronistic citizenship rule" whereby children born in Germany to Turkish immigrants - like Nuri Sahin - were not automatically made German citizens. The law has only recently been changed.
He says Turkish communities also have a strong sense of identity. "Turkey has a form of nationalism much higher than in post-war Germany."
In some parts of the country, especially Berlin, there are separate Turkish football teams.
"When I was young, we had lots of foreign boys in our clubs. These days they go to their own clubs," says Matthias Heitmann, co-editor of the German magazine Novo.
"You have a problem of integration in Germany - on both sides. Turkish communities not prepared to mix, and German communities not prepared to mix.
"On the one hand the German football league has neglected Turkish youth and foreign youth in general - they were looking out for German boys.
"On the other hand, when a Turkish boy wants to play football, parents do have a say, and as Turkish parents are less integrated, they prefer them to go to Turkish clubs."
He also says Sahin's decision may have been taken for good sporting reasons.
"At the last World Cup, Turkey finished third, so it is quite an attractive idea to play for Turkey."
Turkish football scouts are also known to follow the German leagues avidly for potential recruits.
In his restaurant, however, Mr Yildirim believes Sahin's was a purely cultural decision - and the right one.
"His parents are both from Turkey, so he must play for Turkey. That's the normal decision.
"Mehmet Scholl, his father was from Turkey but his mother from Germany, so that's a normal decision to play for Germany.
"If he [Sahin] decided for Germany, the Turkish supporters [at Borussia Dortmund] would hold something against him and boo.
"Turks must live their own culture. It's nationalism, but a positive nationalism."