Calls and contacts
Apps and media
Cause 1 of 2: There are too many running applications
If you've used many applications on the phone, it may get slow because the applications keep running in the background.
Solution: End running applications.
End running applications
Press and hold the Return key until a pop-up menu is displayed.
Press the end app icon next to the required application.
Return to the home screen
Press the Home key to return to the home screen.