Listed below are steps for changing profiles and to check the running applications on a Lumia 520 Windows 8 phone.
As in all Nokia basic phones they provide the option of changing the profiles, but on this phone there is no option of changing the profile. But you can set the volume levels based on the environment you are using the phone.
Use the volume control buttons (+ / -) where you can see the volume getting increased or decreased. As shown in the below screenshot you can see the numbers 16/30. Also tap on the bell symbol to turn on/off the vibrate mode.
During incoming calls press the volume button to silence the call.
How to check the running applications
You will be browsing too many things on your phone and these applications will still be running in the background which might slow down the phone. To check the running applications press and hold the left arrow button on your phone (not on the screen anywhere) which will show the running applications. You can scroll them by sliding.