Philosophical Investigations, 22.
We might very well also write every assertion in the form of a question followed by an affirmative expression; for instance, “Is it raining? Yes!” Would this show that every assertion contained a question?
No, but it would show that the game of asserting is played in a language that also contains a game of questions. To understand this language you need to understand a language where you can ask questions (is the version of that where only questions can be made a possible language?), as well as a language where you can only produce expressions that in our language can serve as answers, and that in this language can only be put after a question.
If you think about how a language with these two components could come to exist, you have to recognize that questions and answers are in reality part of a more complex game, and not standalone parts of a language.