What are you gonna do today?

Mary: What are you gonna do today?

Nack: I have music lessons this evening.

Mary: Oh. You teach music?

Nack: Yes. I teach playing guitar.

Mary: Good. Can you play guitar?

Nack: Of course, yes. I can play guitar.

Mary: When did you start to play guitar?

Nack: It was about 20 years ago.

Mary: Were you a student?

Nack: Yes, I was. I was a high school  student at that thime.

I was a high school student at that time.