Your first two portals should go on the blue gel puddle and on the slanted wall to the right of the entrance. This’ll send some gel onto the wall, from here, shoot a portal up at the top wall on the left so you can walk out onto the metal girders above.
As soon as you make it up to the upper level, immediately look back down at chamber 4’s gel puddle and place an entrance portal in the gel. Now run up the stairs and look for the long patch of white wall on the left-hand pillar.
You’ll want to set your exit portal here so the blue gel makes it way over to the slanted wall, covering it completely. Now head over to the platform on your left and look down at the floor below you. Fire an entrance portal directly below you then fall off, you’ll be carried onto the gel and then bounce up to the walkway above.
Look to the wall on the right of the walkway and use the portals to make it to the walkway directly above you (be sure to jump through the portal as there’s a sneaky gap between the wall and the walkway itself, and it’s surprisingly easy to fall down from).