In case you need to reset your iPhone to factory defaults, the procedure is really easy. But before start, make sure you have made a backup !
Factory Reset your iPhone procedure:
- Go to the Settings
- Tap on General in the Settings app
- Scroll down until you see Reset and tap on it
- Tap on Erase All Contents and Settings
- Enter your Apple ID and password if needed
The reset process will take a few minutes and you will see the welcome screen after the reset process has completed.