It's up to you to play the group match (imitate the Olympic Games) first. For example, it is divided into four groups with six teams in each group. Each team plays a game, winning two points and losing 1 point. After all, the highest score of each group is 1 team (if there is enough time, it is best to take two teams). Choose two teams and send representatives to draw lots to choose opponents, and the winner will enter.
If the time is long, you can play a league match, and each team will win and lose by 2 points 1 point. Finally, you can draw a standings (imitating the football league) and take out the 1\2\3 with the highest score. You can also imitate the NBA and play the league in two groups. Each group takes the first four playoff games, and the first two choose playoff opponents or stipulate that the first one plays the fourth.