would it be possible to have a space to practice typing the correct words and/or sentence after the question is answered?
I find it tricky to get it right first time
Is this for an app. or for a PC? If the latter, why not just have another window open on your computer and there practice typing sentences that give you trouble. Or better yet, why not copy sentences that give you trouble into a notebook and practice writing them out correctly away from Duo? This will not point out your mistakes for you, of course, but it will give you plenty of practice, which is all that is needed to improve, just as you say.