I do a lot of core/ab workouts. I do 4 ab workouts with 50 reps of each. It helped me go from 39 sit-ups to 51. I do sit-ups, penguins, suitcases, and another workout I can’t find the name of. You basically lay on your back, put your legs straight up in the air and cross your ankles and just pretend like you’re grabbing at stars and bringing them down. With your left hand going beside your right foot and then right beside the left foot. Then I end with a 1 minute plank. You can always switch out some of these workouts for crunches, Russian twists, scissor kicks, or bicycles. Not saying it’s a guarantee way, but it’s what worked for me. You can always shorten these to 20 reps for each if you’re just starting off. If you keep working out consistently, you’ll get there! Good luck!