Learn Spanish (Latin America): A la semana siguiente, el equipo ganó el partido. - The following week, the team won the match.

In Spanish, the preposition a is often used with time phrases to mean "later" or "after" a specific point in a story. A la semana siguiente means "the following week" or "a week later" relative to whatever past event you were just talking about. You'll also see this in phrases like al día siguiente (the next day) or a los tres meses (three months later).

This lesson is about the past perfect (like habían ganado), so why does this sentence just use the simple preterite ganó?

The past perfect is used for an action that happened before another past action. Here, winning the match happened after the previous events in the story (indicated by a la semana siguiente). So, the earlier events would be in the past perfect (e.g., "They had practiced a lot" = Habían practicado mucho), and this subsequent event goes in the preterite (ganó).

Since a team is made up of many people, could I say el equipo ganaron?

No, in Spanish, collective nouns like el equipo (the team), la familia (the family), or la gente (the people) are treated as singular subjects. Therefore, you must use the singular verb form, ganó.

Could I say la próxima semana instead of la semana siguiente?