Screen goes black when opening folders

Hi,

I have a big problem with my Macbook Pro. After my MBP fell my screen stopped working. I could change the brightness but that was it. I manage to connect it to external display and it worked. After few days of work when playing full screen video the video started to appear on the screen and it would disappear after leaving full screen. The colors were distorted. After resetting PRAM couple of times and rebooting in Safe Mode the screen appeared but unfortunately at the same time external monitor died (it does not receives any input from the MBP, the same is when I tried the projector). While booting up the screen with the apple in the middle is flashing like crazy (stroboscopic effect) and then the desktop shows and everything seems great but when I try to open anything it goes black although the action I did worked (for instance the folder I clicked is now opened). With external screen now not working I cantuse my computer :(

Pls help if you can