How can i reset unity to default?

Hello, i was messing with unity learning the program and i installed some assets from the store and when i went to install fpscontrol to see what it was all about it messed my unity up big time. i then created a new project and all my scripts and assets even standard unity one's were messed up giving me errors, i tried uninstalling and reinstalling twice, how can i make it so all my assets are back to normal default and not giving errors