Hmmm. Where exactly are you having problems?
I normally put the transmission to around 300 kmh. I like tight brakes, so I normally have them at 8 and 10, respectively.
Then it is really just a matter of knowing the course, I guess. Nurnburg is really fun, because it is such a long course - which means one has to invest more time into it, learning it. And of course with the changing elevation, the narrow track, and the rather irksome AI makes for some really fun racing!
This race doesn't penalize for leaving the track, or for collisions, so one doesn't have to be as precise as, say, Le Sarthe.
So when I come to an opponent, I normally look at it like this :
Opponent car up ahead - I think of it as an obstacle of the course itself. So which way to get around it? Left, right, or wait a bit. These are normally the three options that pop up in my head. I am concentrating, of course, on the track - what is coming up ahead. If it is a straight, I normally take the way of least resistence, providing it looks like I can accomplish this before a corner comes. If there is more room on the left, pass left, etc.
Sometimes it is more prudent to wait a bit, to see what the opponent actually does. The AI is kind of quirky, and either stays on the optimal path, or suddenly shoots across left or right, for no apparent reason other than to shut you out.
If a corner is coming up before I think I can pass (or I am in a corner), due to the rather lax rules here, I try to pass on the inside. You can do this with more speed than would be possible in the corner because you can use your opponent to "brake" with and get through the corner quicker. It does require some practice, and of course it can result in you spinning of the track, so keep that in mind.
That is basically it, really. The only other bit of advice I can give is that if you reach the long straight in front, you can block your opponents who close in from behind and keep them from passing. It is fairly easy on the NR track, as it is so narrow.
I hope that helps a bit.