Hi all i'm a nikon d3200 new user when i first got my camera it's easy to take photo (example it will focus itself very fast when i press the button to take photo), i lent my camera to my dad to use and when he gave it back to me i realize that my camera will take a very long time to focus and sometimes i must switch to the auto mode before i can let the camera focus. Can I also check with you guys another stuff? Can i know what is the "Fn" button on the left side of the camera? Sometimes i find that i need to press the button before my Camera is able to focus. Please help