in this lesson I have some doubts regarding have or did.. I mean will this be correct if we say I didn't open the window rather than I haven't opened the window or can we use did instead of have... how can we differentiate them...

I didn't open the window. (a completed action) .. It means.. I didn't open the window, but someone might have opened and later closed it. I haven't opened the window. (a completed action but has some effect on the present) .. It means.. If you want to check it still closed because I haven't opened it.