You certainly can form questions in English without the use of a pronoun: 'got a pen?' is one simple example. It may be a colloquialism to phrase a question in this way, but it is not so informal as to be considered slang. Whether or not Duolingo accepts colloquialisms is a different issue.
In English you usually need the verb "do" at the beginning of a sentence if it's a question. If you say "remember your sister" in Enlgish, it is imperative (pamiętaj twoją siostrę).
Unfortunately, you can't form a question by just adding a question mark or adding intonation in English.
Hope that helps :)
In colloquial English you can, although I guess it wouldn't be technically correct.
I keep running into this, and not just with Polish... I'm finding out that my "accent" I grew up with is really more of a dialect! (yah, ferrsherr)
Well you can and there are many examples. Got it? Seen it? Eaten it? Been there? Driving? Walking? Asleep? Awake? ...
So you had the 'puzzle exercise' and there was no "your"? If you encounter such a problem again, can you take a screenshot, upload it to some hosting page and post it in the discussion? Because that would be a major bug.