The World Loanword Database states that ngano was perhaps borrowed from Persian گندم (gandom), Hindi गेहूँ (gehū̃) or a related word.
Translations this long can be complex. Technically, my answer "You're buying how many kilos of wheat flour." should be right.
Any hints as to why it's wrong?
It's much less common this way in English ... so they probably didn't think of it. Report it. Make sure you write "flour" instead of "floor" though. ;-)
HAHA! My bad. I did write "flour." Edited.
And yes, I reported it.
What is happening with DL? I put exactly "How many kilograms of wheat flour are you are buying"