I've tried Erik_S's method but I cound't turn off GI, cos' when I did that whole render was black. So I turned it back on but with selected values and dome light it showed that it is goin' to render for an hour!
So I came back to the old studio and try to experiment with render settings a little bit but those shadows are still there.
I am attaching picture with my GI settings so maybe somebody will help me with fixing this problem.
