@wutboi It's not that bad! It actually has an interesting plot in which I'm still curious about what Nico is off to and what's going to happen next. You somehow had the balls to kill off the goddess known as Sally Jackson. It didn't completely leave out Hazel and co; they weren't just forgotten - something that has happened frequently in other stories.
Most importantly, it's extremely unique. I have never, in my entire life, heard of a three-way crossover between Harry Potter, Percy Jackson, and Ninjago. You don't know what's going to happen next; it's pretty spontaneous and a bit of a roller coaster. You're left in the dark until the next chapter.
However, there are multiple apps and software to serve as a grammar checker which I suggest. My personal favorite is Grammarly, a free computer software that checks quite nearly everything you would need (a Premium is an option, but it doesn't seem worth it). There are lifesavers. Life. Savers.
Also, this is more of a personal opinion, but I think adding longer paragraphs work better in a story. Staying focused on the thought process for a bit more time gives it the more professional vibe and helps you read through it with less difficulty. Describing even the weirdest things can actually be really helpful whilst imagining a scene taking place, like what the room looks like or is decorated. The lighting. Whatever.
No offense to your story, of course. It's quite good, and I'm excited to follow the plot whenever you are able to work on it.