For thin people, the initial intensive physical contact training will lead to temporary weight loss, but it doesn't matter. Pay attention to nutrition, rest and strength training. Stick to it for 4-5 months and gain at least 5 kilograms.
Then you will enter a period of slow weight gain. At this time, you need to constantly increase the intensity of training, stimulate the process of muscle growth, and stick to fitness. As long as you take fitness as your career and do every fitness scientifically and seriously, you will eventually become a handsome guy.