Remove lock Nokia Lumia 520 Step By Step and hard reset.
When You Are Buy the new smartphone you should learn how to hard reset this device. because all of the smartphones have major problem slowly working, the device is hang, only show Nokia logo on screen, any apps are not working.if you follow this post you can solve your device problem step by step. you should backup your all impotent data.
1. Turn Off Your Call Phone Pressing Power Key.
2. Press and hold Volume down key + Power key To Short Time.
3. after few second devices is vibrated Release Power Key keep Pressing Volume down key.
4. when the exclamation mark appears on the screen release all hold keys
5. after that pressing sequence of keys Volume up > Volume down > Power > Volume down
Done.