This is actually very easy to solve. When I was a student, I was young, energetic, and had many unconscious activities. Of course, my metabolism was fast. Plus, I didn't pay attention to my diet, so it must be difficult to gain weight. Let me tell you an experience. If you really want to be strong, you can persist and try. If you want to be strong, you must first have a foundation, so you must gain weight, eat well and regularly. The second important thing is to get enough sleep. If we can adhere to these two points, it will be no problem to lay a good foundation. When you can gain weight, keep exercising every day, that is, keep exercising (but don't overdo it when you are too thin), just pick a few things you like. When your weight reaches the standard, you can use proper training to shape muscle lines. Persistence is the most important thing. If you can persist in the freshman environment, you will surely taste the sweet fruits of your efforts.