Force games to be level, meaning players of the same rank must play each other. That will end cheating 100% because the only reason someone cheats is to try and get higher ranks quicker. Can't do that if your beginner can't play with your higher ranked player.
Make game times only 60-90 seconds. No more 2 or 5 minute games turns. Also please find ways to penalise people who could easily win and just prolong the game to be annoying.