Function keys

Hello 

I have dell Laptop Studio 1555

last two days function Keys F2,F3.F4,F5, F6 , and eject DVD functions  are not working , just few days a go I used F4 and F5 for brightness of screen .Volume function works  ( all 3   ..7,8and9) F1 Works 

I read on line how to fix this but with my knowledge of computer that was *** for me !!! ( Sorry )

I request your help in plain layman language please .

Thanks