t is good to buy Salvage Collector upgrade before the quest. It will allow you to collect the scrap from left vehicles. You have to get inside the EDF base so enter the complex with maximum speed and crush all barricades
Do not fight with soldiers. Just go to the back of the hangar and crush the wall with your hammer to get the mech
With that robot you can easily destroy all buildings in the base
Just demolish all structures and collect the scrap. If you have time, you can easily gather loads of it here. When you will be ready just end this missions by parking your machine on the special carriage
Take control of the turret and shoot the cars that are chasing you. Rockets that are exploding near the cars can be very effective too (there is a chance that you will hit more than one vehicle)
When the guerrilla will destroy the bridge - the mission will be over..