Learn Portuguese (Portugal): As raparigas perderam-se porque o labirinto é enorme. - The girls got lost because the maze is huge.

The verb perder normally means to lose something, like an object. By making it reflexive with -se, the verb perder-se undergoes a semantic shift to mean to get lost or to lose one's way. The girls didn't lose a physical item; they became lost themselves.

Why is the pronoun attached to the end in perderam-se instead of coming before the verb?

In European Portuguese, the default pronoun position in an affirmative main clause is after the verb. Because the sentence starts directly with the subject As raparigas and has no negative words, adverbs, or conjunctions before the verb to pull the pronoun forward, -se must attach to the end.

Could I say ficaram perdidas instead of perderam-se?

Yes, ficaram perdidas is grammatically correct and also translates to became lost. However, using the grammaticalised reflexive verb perder-se is the most natural and standard way to express getting lost in Portuguese.

Why do we use é and not está for enorme?

We use é, from the verb ser, because the massive size is a permanent, inherent characteristic of this maze. If you used está, it would imply the maze had recently or temporarily grown to be huge, which does not make sense here.