Sorry, I don't really have time right now to go over everything that makes up a story and comic because I'm busy working on my own comics-- but!
I do recommend Scott McCloud's book, "Making Comics" because it's one of the few English written books that doesn't shit on manga-styled comics and is just pretty comprehensive. I've been making comics since I was very, very young so I didn't learn from this book, I just think it's a good resource for general paneling, word placement, and comic theory.
Also, I make traditional, comic page format for print and not Webtoons so I don't think my advice would help much in that area. I would suggest looking around for some tutorials through a search engine, Instagram can be ok for tutorials, and Youtube probably has some starter guides. I also believe Webtoons itself has interviews with creators and such? Comics and Webtoons are not the same, even though they have a lot of crossover!
And as a last note, I think "good" is a very relative term, you should just make what makes you happy, and not worry too much about the success of it. If you're new to making stuff, I always suggest starting small, so if you were doing regular pages, I would suggest starting with a 10 page story, COMPLETING IT, and seeing how you feel. This means start to finish, page is made and done with text. (You don't need to release it, you just need to figure out how it feels to finish a comic.) And then, go from there. If you don't like the process, comics might not be for you. In terms of Webtoons, I would say maybe a 5 episode (with about 10-20 panels each episode) Webtoon would be about the same to start with.
Anyways, good luck! There's nothing wrong with being a beginner, starting small, and publishing your work yourself. Never let anyone make you feel shitty for being indie, being indie RULES.