Every female is different, and responds to different things.
Shower heads usually require different settings on them for women to find the one that works for them, and even then, it doesn't work for every woman.
Inserting your finger works if you can orgasm from your g spot, but only about 20% of women can doing that alone. I can't, and I'm way older than you. Maybe as you get more experience you'll be able to, or maybe not.
Porn isn't a guide to sex, or shouldn't be. It's all fake, and the actors fake orgasms, and that's not what real sex is like. The majority of people don't look like that naked, and women take longer than that to orgasm, and men often take longer than that to get hard or to achieve orgasm, and can't have as many orgasms as they show. Don't let porn be your guide as to what is normal in sex.
Your normal may be different than what other women experience - and that's normal, too.