Hi Tobias.
I think Nürburgring could make a good slot track, but personally I would advise you to start small, and work up to it. It can take a while to find out what you like in a track design, so if you're trying to plan a permanent layout, you really need to give yourself some time driving and racing to find out what works for you.
Here's a layout that would fit your space, being 7.02 x 2.97m, including borders.
I think it's a reasonable approximation of the real track layout, but there are a couple of things which some people wouldn't like. First, there are several tight R1 corners which can cause deslots, so with six cars on track that could be disruptive. Second, there is no long straight.
Here's one that avoids most of the R1 corners.
But honestly, rather than concentrating on your final destination, I'd suggest looking at the first steps of your journey to begin with. Maybe buy a simple starter set. Have a bit of fun, learn about it all. You'll soon want to add more track and more cars, but you can build it up gradually and hopefully avoid making expensive mistakes. There is a learning curve involved in this hobby, which is all part of the fun.
So, unless you're absolutely set on having a finished product right now, I would suggest taking a little time to learn the basics and find out what works for you.