How to reset PRAM
Shut down your Mac, then turn it on and immediately press and hold these four keys together: Option, Command, P, and R. You can release the keys after about 20 seconds, during which your Mac might appear to restart.
On Mac computers that play a startup sound, you can release the keys after the second startup sound.
HOW TO RESET THE SMC
Resetting the SMC
Shut down your Mac.
Plug it into your power cord.
On your built-in keyboard, press and hold all of the following keys. Your Mac might turn on.
Control on the left side of your keyboard
Option (Alt) on the left side of your keyboard
Shift on the right side of your keyboard
Keep holding all three keys for 7 seconds, then press and hold the power button as well. If your Mac is on, it will turn off as you hold the keys.
Keep holding all four keys for another 7 seconds, then release them.
Wait a few seconds, then press the power button to turn on your Mac.