Breakdown of Legst du das Heft neben das Dokument?
du
you (informal singular)
neben
next to
legen
to lay / to put (flat)
das Dokument
the document
Questions & Answers about Legst du das Heft neben das Dokument?
Why is the verb legst used here instead of liegst?
Legen means to lay or to put down flat, which is an action where you are moving something to a new destination. Liegen means to lie or to be located, which describes where something already is. Since you are actively moving the notebook, we use legst.
Could I use stellst instead of legst to mean putting?
It depends on the object. German is very specific about how things are placed. Stellen is used when you stand something upright, like a vase or a cup. Since a notebook (das Heft) is typically placed flat, you lay it down, so you must use legen.
Why is it neben das Dokument and not neben dem Dokument?
Neben is a two-way preposition. When you are moving an object to a new destination, these prepositions take the accusative case. Since das Dokument is a neuter noun, the accusative article remains das. If the notebook were already resting there, you would use the dative case to show location: neben dem Dokument.
Why does the sentence start with the verb legst?
In German, questions that can be answered with yes or no always start with the conjugated verb. So the statement you are putting (du legst) simply flips to become the question are you putting? (legst du?).