I suggest you do more: sit-ups,
Lie on your back and roll your abdomen (lie flat on your upper body, then recover your legs and then retract them).
Lie on your back and lift your legs (lie flat on your upper body, slowly lift your legs together to an angle of 45-60 degrees, and then put them down).
High-legged sit-ups (putting your feet on the stool),
Lie on your back with both ends facing up (lie flat, with your upper body and legs raised at the same time),
Lie on your back (prepare to cross your hands on your shoulders like sit-ups, except that when you get up, your left elbow touches your right knee and you lie down when you get up again, which counts as one).
Get on your stomach (keep below the waist and lift your upper body),
Prone at both ends (prone, with upper body and legs raised at the same time),
Lie on your side and get up (lie on your side, lift your upper body and keep it still below your waist), and lift your legs on your side (lie on your side, keep your upper body still, slowly raise your thighs to 45-60 degrees, and then put them down).
Note: Choose 3 movements at a time, and do 4-6 groups each, each group 15-20 times, and rest between groups 1-2 minutes.
Remember to relax, stretch your abdominal muscles, or gently rub your hands clockwise after you finish.
PS: Exercise at least five days a week and take two days off. The effect is very good and quick!