Because people are thin at first and don't have so much muscle, they can't do that standard action. Just like doing push-ups, he is very demanding on the muscles of our chest and arms. He wants to do a very standard push-up. Sometimes some people really want to do it, but their bodies don't allow them to do it. He will be very weak, and if he continues, he will become prone on the ground or unable to get up.
In the gym, you'd better find a coach who can guide you personally. You have already applied for a fitness card, so I think the cost of private lessons will still be spent. At least he can teach you how to use the equipment in a standardized way, what kind of training plan to make according to your physical fitness, and what kind of exercise effect to achieve. He will give you a professional plan, which is much better than blindly exercising yourself.
Fitness is a persistent process. You can stick to 1~3 months from a thin body, and your muscles will gradually develop. Slowly, you will feel that fitness is an activity that makes you more confident and happier, and it is not that difficult.
So it doesn't matter if some results are not ideal at first, because it takes time for our body to change it, just like a car. If it has been driving for so long, it always needs to be given some time to brake. So is our body. There is no need to worry too much. If we persist, we can make good changes.