Why does my phone keep going back to main menu?

My phone keeps wanting to go back to the start page each time I switch screens to all apps, opening an app, or simply swiping the settings down. I have a hard time just restarting or shutting down the phone because it keeps going back to the menu. The phone does have a few cracks from being dropped and sustained some water damage after I got caught in some rain at a festival as it was stored in my purse. but if there's anything that I could possibly do to save it, it would be much appreciated!

Welcome to Android Central! Which phone? Does it have a hardware Home button (like on Samsung phones) or an onscreen Home button?

Water damage is never a good thing for a phone, and is typically irreversible. If you didn't catch the water damage very soon after it happened, there's nothing you can really do about it.