Hi Ramin, Here are two correct ways to say this: Have you finished it?/Have you not finished it? Did you finish it?/ Did you not finish it? You can add yet to the end of any of these sentences (Have you finished it yet? Did you finish it yet?)

Yes, it is :)

But what about negative sentence ? Haven't you finished it yet? Is it correct ?

I haven't finished it yet. (negative sentence) Have you finished it yet? (question) - present perfect Hope this helps! :-) Sara