Wikipedia says that July 2017 Italki has 3 milion users from more than 100 countries and 5000 teachers. This website offers more than 100 languages including endangered ones such as Native American Blackfoot and South African Xhosa.

I think however that among those 3 milion users there are many ineffective accounts.

(1)It is fully impossible to tell about the exact members of Italki because so many new people join to Italki daily.

(2) No  I have not travelled to iran.