I wouldn’t recommend buying extra decks
Response from developer
Hey anon739bjsuj86, sorry if it seemed to you that different sets have the same questions. Of course, each set has its own completely individual content. When you create a new game, the free trial set is always automatically selected (small green arrow at the bottom left). To activate or deactivate a set for the round, you have to click on it again, and you can see whether it is then included in the round by the small arrow at the bottom left. Try it again and tell us if this solved your problem. Thanks for your understanding and best wishes from Flying Potato