Were you happy?
Could you do it?
Were you winning?
Will she come?
When we ask a question, we put first the first verb in a sentence. We do it for to be, can, could, present continuous, past continuous and future simple.
Do you understand?
Does he understand?
Did he understand?
In the present simple and past simple, we use do, does or did, when we ask a question.
“Can you hear it?” said the little prince.
“Did you feel sad?” I asked.
“Could you bring me some water?” the flower said.
You can see more examples in the book The Little Prince.