More time needed for timed practice.
Unless you are extremely fast at typing there is no way you are going to get through all 20 questions. Please allot more initial time and more time for each correct answer.
Not to mention the timer continues to count down while duolingo checks your answers.
I find I have enough time, and I often end up with close to a minute left sometimes after the 20 questions are done. I do however have on my speaking exercises which seem to come up more often. Also for languages like korean I often use the word bank instead of typing.