I can't answer that Thomas, Scottish and Welsh people would have to answer

as for football, I can't stand it

All I can say is that I was born and bred in Great Britain and I'm a True Brit
I can say the same about myself but in the case of Germany it's not that simple. I even have an old Aryan certificate (the small one, there's also a large one going back further in history) from my granddad. Shall I appreciate that? Does it make me a "true German"? Who defines that?
Are those 13 to 16 million ethnic Germans who fled or were expelled from parts of Central and Eastern Europe, including the former eastern territories of Germany in the immediate aftermath of the Second World War true Germans?
Apart from those there are millions of people with a migrant background but born in West Germany. Would they not by "true Germans"? Would they if they married a German without an migrant background? Would that have to be a West German or would an East German also do?
To make things even more complicated, if you need to be born in "Germany", is that West Germany then? If so, 17 million East Germans like myself were not born in "Germany" then and, hence, wouldn't be true Germans. In fact, there are a number of West Germans who (still) regard former East Germans as "second-class" Germans.
In sum, everyone who wanted to define what "true Germans" are would find themselves on shaky ground quite soon.