Settings reset after slowdown

I was using BlueStacks and my MacBook started going REALLY slow, then all my settings got reset. I rebooted to see if that would fix my problem, and the Setup program started. I went through the setup as if this mac was never used before, and I decided to see what would happen if I pressed the key that shows all the windows open, and I saw my normal desktop in the background. I finished the setup and am now in the process of changing my settings back to what they were.

Does anybody know why this happened, if there’s a way to prevent this from happening, or a way to revert my setting back to what they were?