Learn Portuguese (Portugal): Quiseste esconder o motivo da visita? - Did you want to hide the reason for the visit?

It is the simple past tense (Pretérito Perfeito Simples) of the highly irregular verb querer (to want). Specifically, it is the tu (you, informal) form, meaning "you wanted".

Why isn't the second verb, esconder, conjugated?

When you have two verbs together where the first one expresses a desire or intention (like wanting to do something), only the first verb is conjugated. Because quiseste is already conjugated, the second verb esconder (to hide) stays in its basic dictionary form.

Could I use razão instead of motivo here?

Yes, you could say a razão da visita. Both words are very common and often interchangeable. Motivo can sometimes sound a bit more like a specific motive or cause behind an action, while razão is the general word for reason.

Why is it da visita instead of just de visita?

In English, we say "reason for the visit", but Portuguese phrases this as "reason of the visit". The preposition de (of) merges with the feminine article a (the) that belongs to visita, creating the contraction da.