'Best friend' usually refers to a friend of the same sex that you spend a lot of time with. 'Special friend' may refer to your boy/girlfriend, although he/she may also be your best friend as well.

i think the best friend he helps for a problems and other things, special friend he talk about unusual situsiations

If you know the difference between the two words "best" and "special" then you have your answer.

"best friend" is one who always gives you happiness , comfort and the other good things, and you too. Anyway your best friend. "special friend" is a best friend who has special personality or ability. :->