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Burn turret, burn!

SPOILER ALERT!

Solution:

1st room:
Open the door with the laser cube.

2nd room:
Bring through the cube by portals.
Send yourself up by placing the cube on the weighted button, when you're up, press the button behind the fizzler. (so you can send up the cube and come up on the stairs afterwards)
Do back down, and send up the cube, come back up on stairs.

3rd room:
Bring the first cube wiht yourself.
Lift up the second cube behind the turrets by the light bridge.
Place the portal on the other side. (now the laser should go through it)
Take the first cube and kill the turrets with the laser through the glass.
Put the first cube on the cube button.
Activate the laser catcher with the second cube.
Make the light bridge go in on the upper part of the portal.
Lift yourself up to the entrance either by jumping and soothing the portal on the white wall in front of the entrance, or by go on top of it next from the 2nd cube and crawl in.

Please let me know, if you solved it any other way!