ONE SIZE DOES NOT FIT ALL.
P90X. Body pump. Turbo fire. All these one size fit all programing doesn't take into account you, the individual. Everyone's posture is different. Your slouched shoulders are not good for overhead pressing. You need more back exercises. You may have tight hips, so getting into any squat position is difficult.
This is where a experienced coach comes in. Please ask any trainer at a gym for a fitness assessment. I know, I will happy to help. Stay safe my friends.