Check out our walkthrough to the Lego City: Undercover:
Make it over past the gate
After you have taken Blackwell back, you will receive a phone call from Natalie. Go now to Chan's scrapyard. First, eliminate the opponents and then, activate the generator. You will have to fill it three cans of fuel: a big one is lying next to the generator and two other are in the green containers. After you have filled the generator, pull the lever. This will start a fan nearby which will take you up.
Up above, activate the lever of the crane. This will lower a pipe fragment and a big Super Brick. Collect the brick and climb onto the pipe (use the same key that you use for getting into cars). Move the pipe over past the gate, into the gap and dash over it to open the passage.
Hint: remember that the stronger, bare-chested opponents can be cuffed only after you have thrown them. After a regular blow, they immediately get up.
The second and the third yard
In the second part of the mission, you have to build a structure. For this, you require the second big Super Brick - in total, you require 21 000 bricks to build a car wrecker. The second brick is in front of a small building that is guarded by a dog. Next to the building, there is a pile of rubble that you need to smash as a miner. Push the fridge over to the left, to the rubble. Behind it, there is a dynamite distributor. Use dynamite to destroy the silver container to the right of the building with the brick. Rebuild it into a dog kennel and take the brick from the house.
After you have built the wrecker and activated it, you will receive a brick that you can use to climb to the higher level and get to the third part of the scrapyard.
In the third yard, at the gate on the right, there is a hook that you can attach your rope to and give it a pull. Jump up and jump into the bud. Destroy the boulders and remove the crate from there. Place it near the gate.
Use the bricks from the crate to build. After it is mover, the vehicle will allow you to jump onto the pillars and make it over to the left, near the silver plane (whose parts you will use to build a teleporting device). First, however, take dynamite under the spot where the orange car used to be, under the hatch in the ground.
After you have teleported into the last section, defeat the remaining opponents. Natalie is imprisoned in the crane, Climb up the blue pipe by the wall and reach her. Then, enter the crane. This is the last activity that you perform in this location, so make sure that you have done everything you wanted to do.