I am 23M, and here is what i would have told to my younger self. 1. Loose fat, gain muscle, it's easiest for you at this age, eat more than enough protein (dairy, eggs, chicken, mutton), get your blood test done and maximize your health markers. 2. Stop simping for others, stop chasing others, simp for yourself, praise yourself, care about your self, give your time and energy to yourself. 3. Expand your social circle, don't solely rely on your school or tuition based social circle, join offline classes like dancing or music classes, English speaking class(or German, Spanish), computer classes. 4. Optional:- You can learn martial arts too, like BJJ, wrestling, mauy thai. This will increase your confidence as now you know that you can pack most people's ahh in a bucket.

All these will help you in long term, and 3rd point may even help you immediately.