I gotta start reading the manga but I haven't yet because idk where season 4 is left off for the manga. Just gotta know the chapter. Or should I read the manga from start?

You should definitely read from the start! The first couple of chapters are similar to season 1, but it later switches from that to something new. There is also mini details that were not shown from some of the accurate seasons/movies that I think would be fun to see!