Im about to lose my mind

Alright, so I don't use Apple products much at all but I decided to take on fixing this Macbook Pro. I have no idea what this person has done to this computer but they sure messed it up. First of all when you start the computer you immediately see an EFI Shell script take place. If you press "esc" during it it will stop and let you enter your own commands. If you let it go all the way to the login page you will be unable to move the mouse or use the keyboard. Nothing to do but hold the power button and restart this process. I have tried booting into safe mode (did nothing except say "safe mode" in the top right corner of the frozen log in page), I have tried booting into another drive ( the only drive available is one that is called "EFI"), I also tried using Transmac to download another Sierra OS onto a bootable USB drive but the computer never even brought it up as an option along side the "EFI" boot, I tried resetting the PRAM the other thing and nada.

Please help me. I'm too stubborn to let this go. I need to know what happened to this computer. :,(

Insert USB alt and power and check if usb display. Possible a bad EFI dump. IF bad dump need to write a new one.