Use the fact that you are an English native-speaker and that you are non-German, that gives you an obvious edge of interest.
I can't agree more with this statement. Depending on the situation, I usually introduce something about being from California / the US fairly quickly. I can tell by body language and other reactions that this often instantly changes a girls attitude from "why are you talking to me, we do not know each other" to "hey, this guy might be interesting and he can't help that he is saying hello, he's a friendly Californian!" Or at least, I imagine it being something like that.
For a long time I avoided this, because I did not want to stand out as "the foreigner." But I have done a complete 180 and honestly I have had excellent luck with it. It gives that that edge that sets you apart from Klaus und Andreas und Jan. Depending on where you live and how often the object of your affection comes into country with your countrymen, she may be genuinely curious as to what the hell this young good-looking English speaker who also speaks German (you do speak German, right? ) is doing in her hometown.
Of course, her curiosity will fade fast if you can't turn this spark of interest into a conversation or a good dance on the dance floor. This I can't help you with.
Two examples, just to show you how silly this can be:
1. Two cute girls are dancing together near my buddy and I in a club. They are clearly part of a bigger group. One girl takes out a cigarette and starts looking for someone with a lighter. She gets several No's, then eventually asks me, and because I had already had my eye on her, I reply (in German) "Neither of us have lighters. We're from California, no one smokes there." She instantly grabs her girlfriend to meet us. This was a long shot and a ridiculous line. But oh man, did it work..
2. My friends leave a club and I am not ready to go home. I stay alone and decide to find a girl to talk to. I see a pretty blonde dancing with a friend. Put myself in the general area. The friend goes to get more drinks. The DJ is playing Californication by the Red Hot Chili Peppers and I notice I am singing. When the song ends I approach the girl and say, in German, with a big smile, "Sorry that I was singing so loud, but that's where I come from!" This night also ended well.
Just use the situation somehow! See how it works for you. Good luck.