About public Beta iOS 13.

Hello, can you help me to restore my original iOS 12.3.1? Because I am not satisfied with public beta of iOS 13. And when I install this on my device ,device become very slow, and it’s turning off 3 time daily automatically. So just I request you to help me how to restore my iOS 12.3.1, or whatever is officially running iOS . Please help me out from this issue.