Cacher is the code snippet organizer for pro developers

MacBook era machines for various things. To do it is really simple:

First, power off your MacBook Pro
Then, when you power up, hold down the cmd+option+P+R keys all at the same time
When you see it cycle round and you hear the startup sound again, let go and let your MacBook Pro boot up as normal.

This on its own may resolve the problem. The other method that runs in conjunction with this involves a little terminal:

Open up Terminal on your MacBook Pro
Type in cd ~/Library/Preferences/ then press enter
Then type rm com.apple.desktop.plist and press enter
Finally, type killall Dock and hit enter again