Translation:Don't put the cart before the horse!
"One thing at a time" is more about focusing on just one thing... But "Don't put the cart before the horse" is about "First things first"... You might be focusing on just one thing but you can be doing the wrong one because you should do something else before. That's why "One thing at a time" is not the same meaning of "Don't put the cart before the horse".
This is the corrected / alternative answer (You used the wrong word message):
"Do not put the cart in front of the oxen!"
The hint word "steers" was not accepted (as always trying to directly use hints) and my answer was marked wrong: "Do not put the cart in front of the steers!"
Why are just the two words steers and bullock in the hint for "bois", but not "oxen" (when this word was accepted as an answer)?
As a non-native English speaker I am lost at all the words like oxen, steers, bullock anyways ;)