I have been trying at this for almost two days now... And I have found the elevator and the two ways you can kill him. But I just don't know how to get the elevator working, or whatever you have to do.

Have you noticed that he gets a little distracted stomping out the lightbulbs, and that you can make lightbulbs and put them in the sockets along the walkways?

To get up the elevator, you just need his head. There's a retina scanner in the elevator.

This is the solution for the entire stage, don't look at the spoiler if you don't want to get spoiled (duh)

When exiting the elevator on the shelf to your left are some blue pipe pieces, take one and bring it over to the crusher (somewhere a bit further to the left). You should see a red and a blue pipe with a piece missing. Put your pipe piece in there. Then enter the room to your left.

You should notice a pneumatic tube thingy. Open the hatch and shoot your portal through it. you'll find yourself in the level 9 security room. In this room you'll find a level 9 card (take it, you might want to use it later) and next to it a machine that produces lightbulbs.

Pull the lever and produce a few lightbulbs (2 should be enough, but make more if you want to be sure) Go back through the red pneumatic tube.

If you look around you'll see a yellow button on the wall, if you press it you'll se a bridge in front of you opening and closing with an alarm turning on and off. Put the bridge down (Alarm off) and place lightbulbs on either side of the bridge in the sockets on the ground. Go hide in the room with the button again.

Adam will now try to crush the bulbs and cross the bridge. While he's on the bridge press the yellow button and watch him die. (Or not? Of course not, that would've been too easy...)

Adam's now super mad that you destroyed half of his body and wants to take half of your body now. Run away from him and find Eve (The giant hydraulic press). crouch and teleport into it, make sure adam sees you.

as soon as he starts running (or should i say crawling?) in your direction turn around and teleport through the iron bars of the hydraulic press. to your right should be a big green button. You know what you have to do.

Enjoy watching adam being turned into a flat pancake and take your new tropy with you (his head).

In the middle of the room on the left side should be an elevator with a Facescanner. Use Adam's head to unlock the elevator.

Thank you so much!
Finally I can keep playing

OMG THANK YOU THAT TALL METAL RE**** WAS SO ANNOYING AND IM SO GLAD HE DIED!!!