I have to charge my battery at least twice a day.

I also see that this user is on an iPhone 6s on iOS 15, so it could be expected the software is draining a lot more battery on the phone (at least that is what I have understood). A battery replacement would be recommended or trying to see if there are any apps that are consuming your battery life. Let us know what route you go with!

Lithium batteries wear out over time, this is why you are seeing your battery health at 80%. Perhaps it is time to have a new battery installed in your iPhone.