If your mobile phone is slow or in any other way doesn't work or respond as well as it should, it may help to restore the factory default settings. This deletes all configurations you've made in your mobile phone.
Find "Reset phone"
Slide two fingers down the display starting from the top edge of your mobile phone.
Press Backup & reset.
Press Reset phone.
Restore factory default settings
Press Erase all data until the function is activated.
Press OK to confirm.
Wait a moment while the factory default settings are restored.
Follow the instructions on the display to set up your mobile phone and prepare it for use.