1. Communicate directly with your boyfriend: tell him your feelings and worries, and hope that he can reduce the time and frequency of playing mahjong and spend more time with you.
2. Suggest him to find other ways of entertainment, such as fitness, watching movies and reading books. Help him develop other hobbies and reduce his dependence on playing mahjong.
3. Make rules: set the time and frequency, let him know your bottom line and principles, and also limit the time and frequency of playing mahjong.
4. Seek help: If your boyfriend is addicted to playing mahjong, which affects your relationship and daily life, then you can consider seeking professional help, such as psychological counseling and so on.
In short, if your boyfriend often goes out to play mahjong and affects your life and work, then you need to take some measures to help him change this habit. Direct communication is a good way to help you understand his thoughts and feelings and let him know yours.