"There is a weird man in front of me."
Translation:أَمامي رَجُل غَريب.
Well, you can use it actually. It would be: هناك رجل غريب أمامي (notice the re-ordering of the words in the sentence). In fact this sentence here goes in line and parallel to the English sentence that Duolingo used here. Literal translation: There/a man/strange/my front.
However, I'm not sure that Duolingo would accept such an answer.