Writing your own story from scratch with your own characters can be challenging. Thats why i decided to do a crossover, im using the mha timeline and main plot points as a sort of scaffolding for my own story. Key events build into and onto filler chapters and vice versa, like meeting mei and getting her to make the EMP/railgun and star saber. They helped to give me a reason to build on Izuku’s, Cyn’s and Mei’s relationship (sorry if im rambling a bit). In terms of writing style i cant really help there since everyone has their own style like handwriting, while some may look similar they arent the same. All in all my advice is to make sure you have some sort of plan/timeline for the story since it will help, when planning a chapter write a list of things you want to happen in the chapter. These notes will be a skeleton for the chapter and then the actual writing and developing and connecting those points will be the flesh that surrounds bones. Again i am sorry if this wasn’t helpful and was just a bunch of rambling