If your phone gets slow or doesn't work as it usually does, it may help to restore the factory default settings. All settings and configurations you've made on your phone are deleted.
Press Settings.
Press General.
Press Transfer or Reset iPhone.
Press Reset.
Press Reset All Settings.
Press Reset All Settings. Wait a moment while the factory default settings are restored. Follow the instructions on the screen to set up your phone and prepare it for use.
Press Erase All Content and Settings.
Press Continue.
Key in the password for your Apple ID and press Erase iPhone. Wait a moment while the factory default settings are restored. Follow the instructions on the screen to set up your phone and prepare it for use.