Piers has covered most of this.
I'll just add this. There is no shortage of young people who want to make movies, quite the contrary. It is an extremely competitive industry. My own son is in the business, and I certainly spent several years when he was very young trying to persuade him to find something else to do.
I'd recommend the same to you. If you choose this as your career, you had better be so totally committed to it that come hell or high water, in good times and in bad—and the bad times will be more frequent than the good times—you stick with it because it is what you want to devote your life to.
It isn't just an option or one of many jobs that you can have. If you really want to do this, and you want to excel, and you want to make your mark, it is a life commitment. If you want to be an Olympic athlete and win a medal, you're not going to do it by training once or twice a week. It is a life commitment.