Translation:We are late, what should we do?
Funny you should mention Old English times - This is a video clip of 'Robinhood Men in Tights' (Mel Brooks film) saying exactly that - "What to do?" https://www.bing.com/videos/search?q=robinhood+men+in+tights+what+to+do&view=detail&mid=4D30B7EEE6210530F5B04D30B7EEE6210530F5B0&FORM=VIRE
The second sentence sounds pretty Chinglish to me. "What do we do," "What do we do now," "What now," or any number of things sounds better as an inquiry. "What to do" is normally used contemplatively or rhetorically rather than as a real interrogative: "You're running late for your flight. They don't let you board. What to do? Listen to my five essential steps for saving your trip..."
I've written down all of the answers in Chinese, English and Pinyin from every lesson I have done. Now I come back to practice and they have changed the answers. The answer here used to be: "We are late, what to do?"
Please Duolingo since I have noticed this before with other lessons, if you change the answer, can you leave the old one in place as well, and not make it even harder to get things correct in this course. This is just silly.