Map 1:
After open the first gate, go thought street up to the hill, you will see the the a small gate, open it will trigger a mini horde or you can skip it, by find the secrect key and go thgouht the shop next to it. So now you will see a lange hole with a crane, go the Control room (near the guns and ammo pile) activite the seccorn gate, its will need to fix in the other building nearby (its will glow), the gate will open after 30s. Go inside and close the gate to end the horde or you can rush to safe.
Map 2:
go untill you inside the 2 big building in the middle, open the door will trigger alarm, rush to the other side and turn it off. Now go to the safe.
Map 3:
Go thought 4 water tank and go untill the big lake (the lake with lange view), open the gate on a generator near the metal gate, horde will come, later burning tank spawn, after a few time the seccorn gate turn green you can go open it, tank 2 will spawn, kill it or skip
Map4:
Go thought a train, then city street till you see the Trigger Final on the control tower in the middle at the end. Now you need activite 5 generators (Random order), after that kill2 tank and go to the cable car to win