Learn Portuguese (Portugal): Eles não gostam de dançar na festa.

In Portuguese, the verb gostar (to like) requires the preposition de right after it. Whenever you talk about liking a thing or an action, you must use gostar de. It can help to think of it as meaning to be fond of.

Why isn't the verb dançar conjugated?

When you want to say you like doing an action, you use gostar de followed directly by the base, unconjugated form of the verb (the infinitive). Here, gostam is already conjugated for Eles (they), so dançar stays in its base form meaning to dance.

Where does the word na come from in na festa?

The word na is a mandatory combination of the preposition em (in or at) and the feminine word for the, which is a. Because festa (party) is a feminine noun, we combine em and a to make na.

Could we put não after the verb, like Eles gostam não de dançar?

No, in Portuguese the negative word não always goes directly before the verb it is negating. It must be placed before the main conjugated verb, giving us Eles não gostam.