First of all, you can solve some study problems with her. You can help him solve them, and then show him that you can solve this problem, so that both my parents can solve it. What is wrong with me? Let him learn to study with you, not when you are playing, so that children will not be interested in learning.
You may be tired at this stage. You can preview what they want to learn first, then you can teach him slowly and share with her the happiness you feel when you preview this content, because every subject has the happiness of every subject. You can share with her the happiness you feel when preparing for this subject.
Because he is no longer interested in learning, you can give him more problems that you think are particularly interested in, or that are particularly difficult, and you can let him solve them. You can tell him that after you solve them, you will see that the happiness you get from solving this problem is because when a person sees this problem and thinks that I can't solve it alone, but when he solves it by himself, he really feels it in his heart.