The art looks good, but your story is very cookie cutter. Fair warning, Asura's Bride on Webtoons has the exact same plot (a princess taking the place of her prettier, 'better' sister in a marriage arranged for the sake of peace and getting kidnapped by an outlaw on her way to the wedding). To make that kind of story work, you'll need a solid red herring or, at least, a way to spice things up and subvert the readers' expectations (a Princess Bride approach, if you will ^^). Fantasy isn't easy to write if you want to avoid a plot amounting to little more than a pile of clichés as it requires a lot of world building and a real attention to details. I'd recommend getting a pretty experienced scenarist for this, or at least someone quite knowledgeable when it comes to this particular genre.
English isn't my first language, so I can't help you out, though. Good luck!