I'm thinking you're right. The reasoning is that you should probably recognise that this is a well-known proverb and pick the appropriate saying to translate it.
Failing to do so would sound awkward to the English ear, so I think Duo is right not to accept other translations than the literal proverb.
There are many different ways to pronounce the "r" in Portuguese. Here's a very good explanation: http://blogs.transparent.com/portuguese/how-to-pronounce-the-r-in-portuguese/