[This answer addresses the storytelling part of the question, not the webcomics-drawing part.]
I've found Brandon Sanderson to be an excellent teacher.
He focuses on:
1) "mainstream commercial fiction" as opposed to e.g. "weird experimental writing intended for a narrow audience"; but I think you need to understand this material before doing weird experimental writing, even if that is your ultimate goal
2) fantasy and science fiction; but again, he's focusing on writing mechanics, so I think almost everything he teaches is useful background for most, if not all, storytelling.
3) storytelling mechanics: he deals with how to construct stories, and how to analyse them in order to understand whether they work as intended; he does not deal with "deeper meaning", critical theory of literature as you might expect from a literature course at university, etc.
Start with the basics, covered in actual university lectures:
(skip the introductory minutes where he says things specific to the administration of his course--only his IRL students would care about that)
Then, continue with the awesome
podcast (which also recommends many other resources).