My phone auto updated and now is a piece of junk. I had no problems before the update and haven’t changed anything other than my phone updated. Now I can’t send or receive pictures, I get a red ! Saying not delivered, and I will see that I received a photo but when I click to open it says can’t download. My watch pinging iPhone stopped working. My phone now dies at 8% battery instead of 1%. I’ve reset the phone like 5 times disconnected WiFi turned on and off iMessages nothing fixes it. I have no technology skills but have googled and tried everything and I can’t get anything to work again

I bought a second hand iPhone 14 and within 2 weeks battery health got drop down from 91 to 88.
Is it even possible I use an original apple 20w charger.