1) Who is talking with you? And you could answer saying your sister is talking with you (Mi hermana habla conmigo.) 2) When do you study with her? You only have to say some days of the week or the number of days (Estudio con ella el Lunes, Miércoles y Viernes.) 3) What do you listen to with them? You can say music (Escucho música con ellos). 4) Where do you practice spanish with me? Just say in the school (Practico español en la clase contigo) In this sentence you can add another "español" after "clase" to say you practice spanish in the spanish class. 5) what do you watch with us? You can say you watch the TV with them (Miro la televisión con ustedes.)
