¿Quedamos el sábado? Shall we meet up on Saturday?

How often. Normalmente veo la televisión — I usually watch television; A veces corro con Pablo — sometimes I run with Pablo; cada domingo — every Sunday; dos veces por semana — twice a week. In casi nunca bailo bien (I almost never dance well), nunca comes before the verb, so you don't need no.

juega al fútbol and ¿Quién toca? In English you "play" soccer and you "play" the guitar, but Spanish uses two different verbs. For a game or a sport it's jugar a: Él juega al fútbol (a + el = al; the stem changes u → ue). For music it's tocar: ¿Quién toca? — Who's playing (at the concert)?

haces, veo. ¿Qué haces en tu tiempo libre? — What do you do in your free time? Hacer means "to do" and "to make." To play sports is hacer deporte, word for word "to do sport": ¿Y no haces deporte? The same verb is in hacer fotos — to take photos. Veo means "I watch," a form of ver.

me gusta bailar. In A mí me gusta bailar, you like an action, so the verb after gusta is an infinitive. A mí adds emphasis: "as for me, I like…"

Invito a Lucía y a Carlos. When an action is aimed at a person, Spanish puts a before that person (the personal a). English has no word for it: "I'm inviting Lucía and Carlos."

¿Quedamos? Quedar means "to meet up (by arrangement)." The nosotros form in a question works as a suggestion: "Shall we meet up?" It's the same in Entonces vamos juntos — then we're going together. And Voy a hacer fotos is ir a + infinitive: "I'm going to take photos."