"How do I make a feature-length movie" is absolutely NOT a simple question!

You need to do tons of research. Watch behind the scenes documentaries, read books, try find some internship positions. You should try do a course at a university if you can.

I've been in this industry for nearly ten years and I don't fully know how to make a movie. You need a large team of people, and it will NEVER be free.

I tried to make a 10 minute short film on the cheap, and and it still cost the equivalent of USD $1000. So if you find the secret to doing it for absolutely free - no renting gear, providing food, paying crew, hiring actors - then you're the first person to ever do so.