MacOS – Apps are not opening in Mac

bootcampgoogle-chromemacmacbook promacos

Google Chrome and other apps are not opening, they just bounce and then stop without giving me any error message.

I also re-downloaded Google Chrome and still not opening.

Recently I installed windows 8 via bootcamp and I had to delete lots of useless files I maybe deleted an important file by accident.

Here is a screenshot of the files that won't get deleted from my trash.(possibly important)
enter image description here

Please help me with this problem. And if it requires terminal I'm fine with it.
I'm running OS X Yosemite Version 10.10.1 MacBook Pro (15-inch, Mid 2012)

Best Answer

First step: don't delete "useless" files.

If the first step was not done properly, please continue to the second step.

Second step: Perform a recovery.
This will restore the OS to its original state but will leave your user data intact.