I'm not sure of the exact meaning here (the English translations seem a bit bumpy to me). Would "Of course we eat slowly" also work?
Why is "we sure eat slowly" not accepted? Is there some uncertainty that makes us question it with "surely"? And if "surely", why is there no question mark at the end of the sentence?
Can be different order in this sentence - let us say "noi mancam sigur incet"?