Restoring your device to default settings helps when the device crashes and resets itself or when apps freeze/hang or reset the device.
Performing these steps resets all system settings (e.g. ringtones, sound settings, display settings, etc.) back to their default values. Personal data such as downloaded apps and media (pictures, videos, music) are not affected.
From a Home screen, tap Apps (located at the bottom).
From the Apps tab, tap Settings .
Tap Backup & reset .
Tap Reset settings.
From the Reset Settings warning screen, tap Reset settings.