Ok 3 things first, this is my opinion on the film and how i understand so this is my baseline

1.) Patrick murdering the hookers and the homeless guy are real, he only kills lowly people in society while Paul Allens murder, the shootout with the cops and Elizabeth being killed are just him exagerrating killing those people. Like he overblows his shanking of a homeless guy to a brutal axing of one of his richest rivals

2.) the movie happens out of order, most of Patricks lies and excuses show that he simply takes hearsay and twists them into what he wants to have happened.

3.) the real Patrick Bateman is an actual dork who thinks hes being complex and superior whereas he constantly contradicts himself and in fact occupies a hand-me-down position for his work

my order of events in the film is

-The business card scene(this is where he got the idea of Dorsia from, by overhearing Paul talk about it once)

- The christmas party and inviting Paul out - Als death by shanking

- The 2nd Kimball interrogation(chronologically for me, the first Kimball scene); also where he first hears of Huey Lewis and the News

- Bringing courtney out to "dorsia"

- the first restaurant scene in the opening, where he starts fantasizing having killed Paul instead of Al - the first hookers scene, where he abuses them

- the second club scene with the model, where he starts drawing out his 'murders'

- inviting Jean to his home

- him breaking things off with Evelyn

- the first Kimball Investigation scene

- The apartment (I am simply not there) scene

- Killing the random lady off the street

- The 'shootout' and 'confession' scene

- "This confession has no meaning" scene

Patrick Bateman is an insecure banker who invited Paul Allen out during Christmas. After going their seperate ways, he vents out his frustration by killing Al the homeless guy. Concurrently, Paul Allen disappears while on a trip to London and Kimball questions him. He doesn't want to get arrested initially but over time, he starts conflating Pauls Disappearance and Als murder into one and basically exagerrates on what really happened. Instead of shanking some random depressed hobo, he lied to himself that he believed he methodically and brutally assassinated one of the wealthiest men in New York. He starts abusing hookers at his home. Inspired by Texas Chainsaw Massacre, starts to fantasize scenarios where he kills dozens of them, seen via his sketches. However, after his bathroom encounter with Luis and heart-to-heart with Jean, he starts to get frustrated. And as seen after 2nd club scene in the film, he kills another person again, the woman on the street. He probably overmedicated himself and started hallucinating by the cat ATM scene and confessed to his lawyer that he is a serial killer. By the end, he cannot accept that not only has he not killed Paul Allen, none of his other 'victims'(which Jean sees in the sketches), warrant him any attention or notoriety.