If you are talking about the "Mine area" in level 5, the main objective of this level is to clear the path of all 3 colors of laser to the end chapter crystal so it will open. Those lasers are blocked by wooden obstables, you have to break it either by knifing or shooting (I would recemmend shooting as knifing sometimes bugged out where she stucked at arming knife state regardless of what you do. You will have to restart the game when that happen) Those laser are from Red, Yellow and Green. Red and Yellow area are quite striaght forward, but for Green you need a total of 3 fuses to activae the elevator which is the most teduous part (You will see later).
The first fuse is at the place where you just start off (Blue area) head straight and turn the first right junction. You then will see the first zombie. Behind him/it on your right there is a pile of crate, the first fuse is right there.
Red Area
After you enter the area and left on the first junction and turn right on the second junction (left to collect Fuse 2, refer below) you should see a ramp going up. Up there you will see a blue crystal on the ceilling shooting a blue laser to a green crystal. Follow the crystal and you will found several wooden obstacles blocking the way, just clear the path until it reaches the main goal crysal.
Fuse 2: Ine the Red Crystal area, keep left follow the path for both junction and you will eventually see a ladder you can jump down. Jump down, and head straight you will see a circular ram heading down. Make it all the way down and you should see a small opening on the left, make it inside there head to the end of the cave, the second fuse is on a rock on the middle.
Yellow Area:
After exiting the Red area, turn the first left and head straight and you will see the yellow area. Head inside and turn left (right is a dead end, there is nothing there but zombies) and follow the path and you will see the laser source. This area is quite straight forward, just head straight and you will find the laser and clear the path.
Green Area:
By now you should have 2 fuses if you follow along the walkthough, the last fuse is at this area where you just enter, head straight, when you see a bigger area and immediately look at the right. The last fuse is behind two concrete portable wall on to of a two barrel. Use the path exit as a reference point, there is a column at the middle of a wide area, let's call it "roundabout column". head to 3 O'Clock (or just turn the first right) and head straight make it all the way down (follow the "Elevator" sign to the main objective) and you will see a panel to insert the 3 fuses you have collected. Put them all in, activate the elevator, and you have to back track all the way up (Yeah, seriously. Why can't she ride the elevator with the crystal?). After make it all the way up when see the "roundabout column" on the point you standing, head to 3 O'clock again (or just turn right) and you will find the laser source that you just brought up. Again, clear the path and the exit crystal will be activated. Just enter the crystal and end game.