I read this story 8-15 years ago in German. I'm not sure but I think the book had 2 short, totally different stories in it.
The story was about a man who was sent (I think kinda forced to go) to a planet where he should play a game everyone on that planet plays. I think the goal was to beat their leader and conquer the world like this?
The better you are at the game, the higher is your position in the society. I remember that at the end he was playing against the leader and they had a long back and forth game, but I'm not sure who won.
They played the game on a different planet that had only one stripe of forest around the whole planet and a fire that goes around it. But thats only the location they were playing.
The man was chosen because he was the best player in every game if I remember correctly.
The game was a board like game where you have troops or armies that you move around. It was not an easy game everyone just could play.