First of all, we should convince ourselves that it is her advantage that our girlfriend has not grown up. Since we choose to be together, we must learn to tolerate each other, no matter the advantages or disadvantages, as long as we can make each other comfortable, we must work hard. After all, no one is perfect, what's more, she is still a girl, and she hasn't grown up to prove innocence and has little experience. Faced with such a situation, as boys, we should regard it as an advantage, so as to get along better, make ourselves comfortable and get along.
Secondly, we should know how to take on more responsibilities and encourage and spur our girlfriends with our own Excellence. None of us is born mature and steady. Some people are still immature even when they reach a certain age. Just like a child who hasn't grown up yet, we can't force them to grow and progress, but we can only slowly influence them and spur each other with our own Excellence and maturity. As long as girls really want to be with themselves, they will work harder and harder because of their Excellence and maturity.
Third, when appropriate, let your girlfriend make up her mind and take responsibility. Feelings, after all, are not playing house. Being in love can allow some childishness, but never allow childishness, let alone being in a state of growing up all the time. Two people should be equal, so don't help your girlfriend with everything. Even if she makes a mistake, she will never grow up, so you still need to work hard to make your girlfriend a better person.