Mom thinks her boyfriend is immature. What should I do?

You can just tell your mother that he saw you. He's a little stiff. Life is not like this. Tell his mother about his heroic deeds and change her mind.

In addition, it's mainly because your boyfriend will come over to do something, don't call your mother, call your aunt more, be careful not to talk, be diligent, help your elders whatever they are busy with, and see what's wrong at home. To please your mother-in-law, you might as well analyze your mother's hobbies, then please her appetite and coax your mother, so that masculinity will become gentle and considerate.