Talk with Tilda at the second bar location and ask her to explain the game again.
This is an easier version of an actual card game, Durak, made in a way to heavily benefit the player. My general advice is to look for the trump cards and collect as many as possible till the cards on the table run out, so you could beat all the cards the NPC has on hand and throw at them unbeatable cards yourself. Start from lower digits so when the NPC tries to use your cards against you, you could beat it with your higher-tier cards.