My friend, your chest muscles don't hurt, and the reason why your arms hurt is that your arms are weak, especially your triceps. On the other hand, because your posture and force point are wrong, your force point is on your arm, not on your chest muscles. When practicing chest muscles, you must have an action of expanding your chest and closing it, and fully open your chest. The two shoulder blades should be locked backwards, and the weight should be slightly larger. Basically, one group 12, 4-6 groups can increase the volume and circumference of your chest muscles. Do you think your chest muscles are much bigger than your arm muscles? Naturally, your chest muscles will be much bigger than your arm strength, so the load of practicing your chest muscles must be much bigger.
In addition, if you want to know whether your chest is muscle or fat, you can contract your chest muscles and see if there is much subcutaneous fat. If you have more, you should lose fat; Because in the case of low body fat content and high muscle content, the shape, outline and line sense of muscle are basically visible.
In addition, the abdominal muscles you mentioned are actually the parts that torture people. If you want to train six beautiful and clear abdominal muscles, you must reduce your body fat level to a very low level, and abdominal muscles are the most anti-fatigue muscle group, so you need to make great efforts and exercise for a long time, such as sit-ups and hanging your legs.
I hope my answer is helpful to you!