This is what you should see when first entering level 5
Note: I have cheats activated, but you don’t need any cheats to reach all secrets.
Look to the right of the toxic waterfall and fire your teleport gun
First secret found
Note: Head to your right past the closed off area to the blue door to get out of the toxic pit again
Go through into the corridor with the hole on the side
Go to the hole and fall down
Head to your left until you reach a dead end
Walk into the wall
Secret 2 also found!
Approach the toxic waste and shoot your teleport gun at the location on the picture
Then teleport onto the location on this picture
Finally onto the platform shown here
Secret 3 done!
Look to your left and drop down
Turn around and look at the bridge, there should be a small room which is Secret 4