I get it's a rant and all, but from the limited information you provided this 'asshat' did a perfectly legitimate thing by inviting you to a roleplay. You have the freedom to turn such an offer down if you're not interested in said RP, of course, but I'm not really sure what the purpose of this thread is. You see, you're asking for someone to teach you to play pretend and then interact with other people playing pretend. If your inquiry was as vague as your rant, you must understand it is difficult to understand what you are looking for.
I can only hypothesize what would trigger such a reaction. My guess is that it's shame. You do not want others to see your writing while you feel you're not ready. You're looking for training wheels or a shallow pool, so that if something goes wrong there's a safety net. If that is so, let me ask you why you would feel shame over being judged on playing pretend by other people playing pretend? Our goals here are to entertain our selves, for some to escape the stress of their outside lives. If you can do just that, which trust me, you probably can, where is the shame in that? Sure, different roleplays will have varying requirements. That doesn't really matter. It's not a status thing. and everyone who treats it like a status-thing is a shallow cunt because they forgot what roleplaying is about in the first place. Want to know who isn't a shallow cunt? The guy reaching out to you and inviting you to a roleplay. He is someone who wants to share his experiences with you directly. I can think of no better teaching method.
Or maybe I'm wrong and something else is the case. Who knows.
Nonetheless, if there are some specific topics you really feel you need to dive into,
@Brovo wrote two guides that go into detail about how to set up posts and characters;
https://www.iwakuroleplay.com/threa...sts-the-action-reaction-wheel-and-more.87700/
https://www.iwakuroleplay.com/threads/characters-101-roles-relationships-combat-and-more.93852/
No guide is an end-all, but these are certainly good places to start.