Questions about "what to write about" are off-topic. But your question can be also interpreted as "how to start a novel" and so I'm going to answer that one.
First a misconception on your side:
I know nothing about writing.
This sentence is only excusable as a citation. But your name is not John Snow. So forget about it, because writing this question proved that you know something: Adding characters to sentences and sentences to paragraphs. Welcome to the club, you are a writer ;)
Now, you have read over 70 fantasy novels. That's a good start for writing a fantasy novel yourself. You know the basic concepts what is expected in a fantasy novel (or at least what you expect) and that's a good start.
Even more, you have a hero, a villain and a kind of plot. Give your hero and your villain a name, jot down how they look like, what they are good in, what they are bad in, open your word processor and go!
Yes, don't think too much. You have a gut feeling. Listen to it, it keeps you writing. Don't bother about rules, what should be done, what should be avoided. Just write how you think it's fine.
This might be counter-intuitive, because we have here a whole site with all these nice tips how to write a better story. But the truth is: Before you do not have some experience in writing all these tips will not help you. They even can be dangerous and kill your creative voice. Nothing is worse than follow rules you do not understand. And you cannot understand them without some experience. Even if they sound totally logical when reading them.
So follow the good old writer's principle: Just write! And if you stumble over more problems after you started your novel, come back and maybe we can help.