Help me fix my keyboard

Hello. I really really need your help. Actually, my keyboard works fine. But.. my arrow key is suddenly changed. I use Lenovo laptop and when I press up and down button, It change to set brightness of the laptop. and when I press left and right button, it change to set volume. I have press 'Fn + NmLk' and only the numpad on letter keyboard change. but arrow button didnt change.. Pls help me fix this.