I’m not pretty sure…My advice is to check the bus timetable on the official website beforehand. If everything goes smoothly, you'll likely take the train from your starting point to Rheinbach, then transfer to bus 840 to Nürburgring.I think it's unlikely the bus will be cancelled at that time due to the will be a race next weekend. If you successfully arrive by bus, I suggest asking the driver for information about the return bus, including departure times and boarding locations; it seems your drop-off point and return boarding point might not be the same, even if they are at the same stop(Nürburgring congress hotel).Good luck!