Regressor instructional manual novel readers

OK so i read the novel until chapter 803 but i didn't read it for about a good two years now so i kinda forgot everything but i don't want to reread it because i really wanna read the side stories as fast as possible so can you please tell me and remind me about everything that happened until chapter 803 please
(Ps you don't literally have to tell me everything just the important stuff if you want and yes I did repost this question I'm desperate ok)