does the macair have arabic keyboard originally? if not how i can get it?
Nobody in these forums represents Apple or any store, so to find out whether you can buy something you will need to contact stores directly yourself or consult their websites. For example, you can find an arabic macair here
The website for the US online store makes it clear Apple does not sell them via that channel.
If you contact an Apple retail store, you can ask if it is possible to get one as a special order: