I'm pretty much a novice but I think you may skip the bracketed _you_ because it's idiomatic to skip it when its clear from the conjugation. E.g. (You) go and (you) find him.
Also guessing that he was using material and not learning at an institution, I should have used केन (using what) Or just asked कथा (how).
कुत्र = where (?)
पठसि = studying. When you want to use "studying" with "you"; with "I" it would have been "pathaami" (पठामि) iirc.
संस्कृतम् = Sanskrit
So, it should roughly read "Where are (you) studying Sanskrit?"