Learn Dutch: Herinner jij je de vakantie goed? - Do you remember the vacation well?

The verb "to remember" is reflexive in Dutch: zich herinneren. This means you must include a reflexive pronoun. In this sentence, jij is the subject ("you") and je is the reflexive pronoun (like "yourself"). You are literally asking "Remember you yourself the vacation well?".

Why is the verb herinner instead of herinnert?

Normally, the jij form gets a -t at the end (like jij herinnert). However, when the subject jij or je comes after the verb—which happens in questions—the -t is dropped. That is why it is Herinner jij.

Can I use the unstressed pronoun and say Herinner je je de vakantie goed?

Grammatically yes, but saying je je right next to each other sounds awkward. To avoid this double sound, Dutch speakers usually use the stressed subject pronoun jij instead, making it Herinner jij je.

Where exactly does the reflexive pronoun je go in a question?

In a question, the verb comes first, followed by the subject. The reflexive pronoun always stays as close to the subject as possible, so it goes immediately after the subject jij, and before the object de vakantie.