well, the ring, when open to the public, is considered as a public one way unrestricted toll road.
so if you come by the road with your car, you can drive on it, but there's no training, unless you subscribe to one of the "schools" there (the one I see all the time charges 400€ for the day and you get to drive a 200hp RWD oldschool alfa romeo, but I think you have to pay for your laps too)
basically, it doesn't matter if you know the track from games whatsoever, on your first times there, better drive slowly, carefully, because it has nothing to see with anything you can experience in any video game.
there are many crashes and it's very dangerous and tricky, and that's when you're in a car, you can go everywhere on the internet you will never find anyone who'd recommend you to get there on a bike, specially for your first time.
I've been there a few times when it was raining, so there were no bikes, there were crashes, but no one seriously injured.
both last times I went there, it was sunny days, and several bikers were seriously injured, one got stuck under a car and had to leave in an helicopter.
it's pretty cool to drive there, but in a second, things can go pretty bad so you allways have to leave yourself a decent safety net, don't push your car or self to the limits and allways expect the unexpected. In a game you don't realize how blind the corners are, so once you're there, it's easy to lose your marks and forget about where exactly you are, then you ask yourself the question: "is that a left or right hander after that crest ? where the f**k am I exactly ?" while you see a nissan sunny closing up from behind at incredible speed, battling with a porsche GT3 and a yamaha R6.
so, of course you got your "pride" and you want to drive, but things can go so wrong in an instant that you better go easy, and you'll find out that no one would blame you for that, cause that's how everyone does at start, more or less, depending on the driver, the car or the experience.
and that's no less of a fun anyway, after a few laps you'll start getting abit faster, eventually, then get confidence and enjoy the track a different way.
I didn't do that much laps, only 6, so some places still scare me alot, like the fuchsröhre that seems to go down straight to hell, schwedenkreuz, it'll take me hundred of laps until I can get in that one with confidence, and the list goes on...
there are a few corners I can say I might at least have the line right, maybe not on the video, due to all the faster cars I had to let pass me, but I know I'll do ok in adenauer forst, probably hatzenbach, wipperman scares me a little bit but I think I got it right, I know I can have aremberg right, as well as ex-muhle wich looks allright with a not so powerfull car, both karoussels are pretty much allright, it's not like they have 5 lines so... just remember to never get out of any of em too early!
you wouldn't drive fast on a road you don't know and you know as dangerous would you ? then it's the same thing, wether you know it or not from a video game, get there as if you never seen the track before, try to remember the general idea and drive carefully, so you'll be fine.
you can also rent cars round the track, 1 day costs between 150 (suzuki swift ring tuned) and 1600 (porsche GT3RS) euros a day for specially tuned cars, I can link you to websites if you want.
you can have a megane RS (renault) for about 500 euros a day, or a clio RS 192 for 400, VW golf GTI, BMW M3, you name it.

original tuner ---- garage setagaya ---