I just used sonata as a pronoun which means "you" and used no after it that it belongs to you
Just like watashi?
わたしのなまえはなんですか。
watashi no namae wa nan desu ka.
OK can I say nani which means what?
なまえはなにですか。
namae wa nani desu ka.
I don't know why they use
nan.
Look at this website, in the question they used "nan".
and in the vocabulary list on the next page they state "nani" as "what".
Vocabulary, Grammar - Lesson 2 - Language - Kids Web Japan - Web Japan