My suggestions for Prisoner of Azkaban:

I would like the movie to be more colourful if that’s possible, especially the scenes that play outside at bright day are way too greyish
I always hated that the patronus has a slight delay in this movie, like Harry screams “expecto patronum” and there are these awkward 1-2 seconds where nothing happens
in the book quidditch takes a big part because it is Oliver Wood’s last year and he still hasn’t won the quidditch cup, obviously you can’t add scenes that where never filmed, but maybe you could add one or two voice clips from previous movies like “be careful, Harry” to show he is at least there
the same for Cedric Diggory and maybe cut out the actor who played the Hufflepuff seeker, cause it creats a continuity error
the screams of Harry’s mother need to sound more terrifying and less like it’s singing
when Fudge tells Mcgonagall the story of Sirius’ betrayal you could show footage of their death
I hate the scene where the fat lady tries to break the glass it’s so unnecessary and painful to watch