I had just started training when I was around your age (about 3 years ago) and I thought about these Things too. You've started training at a good age. For now, don't worry too much about these Things. Find a proven program that can help you achieve better technique on the big lifts. Lift with a simple program consistently and eat healthy foods for the most part. All you need is time, if you dedicate to a proven program in a few years you can be very strong.