Building strong and quick muscles?

this summer a friend and I (16 yo) have decided to make use of our school's weight room. we want to get fit for sports and girls!! It's pretty well equipped, and we have an older friend who is an insane athlete to work out with. We usually go from 9-11, the main part of the workout being probably 10-11, the time before that is like warming up, stretching, jogging, etc. we start early and do fartleks and running around the track some days, and once or twice a week I run 5 mi to school. My question regards things like diet. I usually have muscle milk or just milk/chocolate milk after workouts, and a small breakfast (yogurt, juice, fruit) before. some people there who are really strong use stuff like amino acids and "cereatine" supplements, are these safe, and what do they do? are supplements like muscle milk and that really beneficial? also, I am always sore after the workouts for like 3 days in the muscles we worked, how can I lessen this recovery time?