score:7
You can use any of the official on line public transit planners in Germany to find out schedules, and you can assume those to be correct.
The Germans really want you to take public transport to that game. So much that free travel in the entire VRR area is even included in the ticket price.
So you not only can count on being able to get to/from the game using public transit, you do not even need to buy a separate ticket, as Duisburg is within the VRR area