The reason why pull-ups can't go up is that your latissimus dorsi is underdeveloped. If you want to make the pull-ups suddenly qualified, that is the hanging bar. Hold the crossbar with both hands and pull it hard. Although you can't get up, you can exercise your latissimus dorsi, and it will be fine after a long time.

As for the best way to exercise, I'll give you a set that suits you, simple and quick. You are too young to lift dumbbells or equipment, otherwise your figure and development will be affected and it will be harmful to your life. My suggestion is to take time to run 5km every morning, noon and evening, preferably within 23 minutes, rest after dinner every day 1 hour, and start push-ups for one hour. In this hour, do it slowly and do your best. Stand up when the time is up. Push-ups must be standard, and it is better not to do them if they are not standard. Hold on like this for a few months. If you can run for 23 minutes in 5 kilometers, please contact me and give you the next plan. I deducted 3 6 1 0 6, 9.372.