Thank you in advance for answering my questions. I'll make an exception. First, at 14 years old you should be watching everything and everybody. I don't mean movies. Watch people, try to figure them out, try to listen to the cadence and content of their speech.
People are simply characters without a plot.
They're your best place to start. And no one thinks a 14-year old is paying attention, so they're likely to let you watch and listen. And of course you should write. But I wouldn't get too hung up on writing a whole screenplay just yet. Just write whatever you feel like.