Damn it was quite annoying at times, but at least I learn quite quickly. After a few tries, I managed to complete the last level on Nightmare.
It was a fun experience, but I am kind of done for now. I don't feel like completing the Predator, and Alien campaign just yet, because the amount of work that needs to be done can be quite frustrating.
So until the next time that I play this game and attend to the other campaigns.