Age? Hang in there. Combine your sports hobbies. Contact some sports groups in the same city. Protein is high in the diet. Fix some items every day and gradually increase them. As long as you are healthy, you will gradually become strong. Not too thin.

For example, dumbbells every day, starting at 8 pm, 20 at a time, do 5 groups.

Push-ups, starting at 4 pm every day, once 10, do 5 groups.

Frogs jump every morning, once every 20 meters and five times.

. . . . . .

Do joint activities and warm-up before each departure. Prevent injury. . . . . .

Leg press, shoulder press, jogging every day 1000m, swimming. . . . . .

According to your own time and conditions, science is step by step.