I think the time limit is quite efficient and a good, decent amount of time, personally, many people have tough times doing these quizzes and do not excel as well as we do. I am working on making more, you can tell by the title have "#1 in it, meaning there will be more to come.
The yellow box, is not very efficient in this quiz, but since there will be more quizzes to this... Some of them will need these yellow box, in conclusion, I think we should add the yellow box and that is the reasoning behind why I think so.