Learn Italian: Nasconditi dietro il muro, presto! - Hide behind the wall, quickly!

Nasconditi is a command using the reflexive verb nascondersi (to hide oneself). In Italian, when you give an informal command (the "tu" form), you attach the reflexive pronoun (-ti) directly to the end of the conjugated verb. So, nascondi (hide) + ti (yourself) becomes nasconditi.

Why does "to hide" need to be reflexive here?

In Italian, if you are hiding yourself, you use the reflexive verb nascondersi (literally "to hide oneself"). If you were hiding a physical object instead, like a key or a present, you would just use the standard non-reflexive verb nascondere.

I sometimes see dietro combined with a preposition. Why is it just dietro il muro here?

When dietro (behind) is followed by a noun like muro, you can use the definite article (il) directly after it. You might also hear Italians say dietro al muro, which is also correct. Just remember that if a pronoun comes after it, you must add di (for example, dietro di me meaning "behind me").

I learned that presto means "early." Why is it translated as "quickly"?