There are a few things you should try first when you experience problems with your device:
Restart your phone to turn off all running applications and to remove memory blocks. Remove and reinsert the battery and the SIM card. Then restart your phone.
Update your phone to ensure that you have optimal performance and the latest enhancements. Read more about how to update and find latest software version.
Reset your phone to its original settings to remove memory blocks: Settings > Backup & reset > Factory data reset > Reset phone Don't forget to back up any important data saved on your phone!