Translation:If only you knew how long we have been asking.
I think this was the hardest sentence yet to predict the English. I knew exactly what it meant but i knew the answer would be nothing like a literal translation. Well I say exactly - I went for "...how long we've been asking him" and it was wrong. And I'm not sure enough to mark it as a mistake. Usually when you ignore a "lo" it's wrong. So it accepted "... asking it"
"If you knew" is now accepted.