Aww, I'm humbled. I'm glad you enjoyed it. I left comments beneath every video that give some insight into my own creative process so hopefully they'll be helpful to you too.
My advice for any first project would be to start off small only a few maps before going big. Plan out the story before you start, the inbetween parts can be altered/tweaked as you go but ideally you should know where your story is heading. If you're struggling with triggers or how to do a certain thing then looking at the blizzard campaigns can help a lot, they're very rigourous in how they trigger and code stuff and you won't need to be as tidy but it'll give a good look into how to do things properly. Lots of small polish touches can add a lot to how good a campaign looks, for example deselecting units during cutscenes, it's a small detail but it looks amateurish if you don't do it.
Either way, all the best and good luck with the campaign.