Pretty self-explanatory achievement.
Simply load up a puzzle of your choice (
I recommend the easy-difficulty puzzle Turtle) and complete it
20 times in order for this achievement to pop. If you (like many people) don't really know how to play mahjong, you can always use the
hint button as the hints are unlimited and don't stop you from finishing puzzles and unlocking achievements. You can speed up the process by clicking
New Game instead of
Choose Puzzle after a completion as it will create a new game of the same puzzle and saves you the time of opening the menu and creating a new game manually.
Good luck, y'all!