You could take a bus and/or train with one change to Brühl but the shuttle buses of Phantasialand do not run at night so you would need a taxi from there.
During that time of the night with a remote destination like yours, I would probably just take a cab directly from the airport.
I‘d estimate the fare to be around €60.
The Matamba Hotel is so nice, make sure to visit the bar there too. I spent a lot of great times at this beautiful bar.
I would check on www.bahn.de if there are still trains running to Brühl and Taxi from there to the Hotel. Maybe you could also contact the Hotel, explain them your situation and possibly they would have a service to pick you up or alternate options as I am sure you would not be the first guest that is arriving late and Phantasialand is great when it comes to customer service.