"Dunaj" is a Polish surname meaning "dweller near the Dunaj River" (which is another name for the Danube River). The "Dunay" or "Dunai" part of your name may be a variation of "Dunaj".
The "-evich" part could be a slavic patronymic, meaning "son of".
I'm not entirely certain what Jews look like in Argentina, when you say that "we don't look like jews", but here in the U.S. we can look like just about anyone else.
-- Nanaea