When i will recieve my visa after my intrview was completed in the usa empassy in damascus ( imgrant visa )?

well, the NVC doesn't, and can't, actually approve your immigrant visa. all they do is process the petition itself and schedule it for interview in Damascus. Once you get to that part, what happens depends on the interview itself. Assuming you have everything you need for a final decision, it can still take a while depending on whether the case goes into Administrative Processing. If it does, you'll probably experience delays. How long is very difficult to predict. Then there are the current problems in Syria. If things deteriorate further, it will probably affect business at the embassy.