Valley of Suspicion isn't really that hard. It just requires you to use Goggles to find keys.
Some keys are hidden though but it might not be plainly obvious where they are. So now we start a very breif walkthrough of Chapter 5 Act 2.
Map of the Second Block
When you start the first block, its pretty simple that you basically use the goggles to find the right switch to open the door. When your viewing through the goggles, look for a green circle. If you see a green circle, you can press that switch to move on. Eventually you will reach another set of switches that can activate traps. Just use your goggles to find the switch that doesn't contain any trap near it, and the gate will open.
Kill Bil & Get Key!
When you reach the next block, you'll have to deal with finding 4 keys to open a gate. The first 2 keys are located by defeating the Bil De Vears. The other 2 keys are located at the entrance by destroying the two traps that shoot at you. Again you'll eventually reach up to another 4 key door, and you'll just need to defeat the Bil De Vears to obtain the keys. There are 4 distinct Bil De Vear areas so just walk up to those places and defeat them to get the keys.