This is the LAST part of Portal.Once you complete this,you may get the heartbreaker achivement.
Wake up and smell the Turrets
Get past the sewers and at the end,you see a wall thats portal-friendly.Get there.Now just try to portal out of the gooey but not lethal water.Once you get to surface,you hear an alarm and turrets will shoot you to death.
Try to take cover as they shoot you and while they shoot,put a portal behind them and put another near you(Wall or floor,your choice).Then KO them!
Once you take out all of the turrets,find the turret thats in the highest floor.Put a portal in that aclove and put a nearby portal.Once in that location,scan the room for a slanted wall.Once you find it,put a portal on top of it.
Now here's the trick to find a few more turrets:Put another portal near you.Then pass it,you may fall and put another portal in time before you land.You are flinging in the sky.Your super jump is not high and fast enough to get where you need to go but enough to make you target Another slanted wall that's even higher.Put a portal there and do the same for the other portal.
Now you have enough to reach the higher ledge.
You Lose,I Win
Now quickly go behind the turrets as they will be delivered to kill you,then KO the 2 turrets.Now you have to jump your way up a hole.Put a portal on where you will jump on the hole and put another on the floor of the main room.Now jump on the portal and you may find that is enough to build your way up the hole.
Now just aim yourself to the next platform and then follow a catwalk followed by some doors you just need to open.
The Boss!
Now you get to battle the boss:GlaDoS
After her talking,put the core near the incenarator then portal the room with the button.Put another portal near you.Pass through the portal and press the button.Quickly put the core in the incenarator.
Whoops.....
GlaDoS explains that the core you just destroyed was a recent morality core that stops her from filling Apeture laboratories with neurotoxin and other deadly gases.
Now she gives you 6 minutes to finish her off and a rocket launcher to dodge.This bot gives you an advantage cause you can't shoot her cores out because its a portal gun.Now shoot a portal to a wall that is available to shoot GlaDoS.Put another portal that is on line to GlaDoS.Now make the bot shoot you a lined with the portal.When it locks you,dodge quickly and it will shoot GlaDoS instead.
The next core is on a pipe.Portal to the core and incenarate it.Do the same 2 more times and you win the game!