Could this be "the window opens into the yard"? sounds more logical in english to me. (( Though I often question my English :/ ))
According to Garzanti "cortile" means: court, yard, courtyard. Please add the two other translations to your files.
The hover says "il cortile" means "the backyard" too, but it was not accpeted in my answer.
This is where I question my English...Can a native English speaker kindly explain to me what "onto" means here? Does it mean that the window faces the yard and that when you open it, you see the yard?
It's a fairly unusual use of the word "onto" (at least in the US - but it still sounds natural). And yes, it means what you suggest. An equivalent phrase would be, "The window overlooks the yard."
Or as suggested by jeslam1 in another variation of this question, the window opens OUT TO the yard.
About (aspettiamo nel cortile) i translated it ..... on ... which duolingo told me it is wrong and the right answer is (in) .... and now i translated the sentence ( the windows opens in the courtyard) .... which is wrong also .... confused !!!!!!!