The calculation looks good.

One hint you can also calculate how you started. But you have to use both yields.

5000 kg *17/63 = 1350 kg. Then 1350 kg/(0.92*0.97) =1511,9 kg NH_{3}

Your question I don't understand where you get 2 NH_{3}?

In the last line I also dont understand 21598 *57 *0,93 = 20086,5

Probably you have also to calculate the oxygen consumption and from this the air consumption. Air contain 21% Oxygen.