The question "Are you seven?" is asking if someone is seven years old. A possible extended response could be:
"No, I am not seven years old. I am actually [your age] years old. Seven is an interesting age because it's typically when children are in the early years of primary school, often learning basic arithmetic, reading, and writing skills. It's also an age where they begin to develop more complex social skills and can engage in more structured play and learning activities. At seven, children are usually full of curiosity and energy, eager to explore the world around them."