If you are experiencing recurring malfunctions with your smartphone, it might be necessary to performed a hard reset.
Backup your phone
Before you perform a hard reset you should backup your phone, as all your personal data and settings will be erased. Even if the hard reset does not affect the data stored on the SD card, it is advisable to remove it (unmount) before performing this operation.
This procedure is the same for most Android phones.
Go to Settings > Accounts > Backup and Reset.
Tap on Factory data reset.
Note that: On some phone, this option can be accessed from the privacy settings.
Turn off your device.
Press and hold the Up volume button and Power button simultaneously for a couple of seconds.
Wait until the logo is displayed to release the Power button (but keep the volume button pressed).
A menu will then be displayed.
Move across the menu using the Volume keys.
Click on Wipe Data/Factory Reset and validate with the Power button.