Для переформулирования утверждений в вопросы в английском языке, использующиеся с глаголом "to be" в настоящем продолженном времени (Present Continuous), необходимо переместить форму глагола "to be" перед подлежащим. Вот как это выглядит на примерах, которые вы привели:
- They are playing the piano. - Are they playing the piano?
- I am talking. - Am I talking?
- He is writing. - Is he writing?
- She is dancing. - Is she dancing?
- We are jumping. - Are we jumping?
- She is walking. - Is she walking?
- We are watching TV. - Are we watching TV?
- You are driving a car. - Are you driving a car?
- I am reading. - Am I reading?
- He is making a sandcastle. - Is he making a sandcastle?
- They are painting a picture. - Are they painting a picture?
- You are singing a song. - Are you singing a song?
Этот способ формулирования вопросов помогает уточнить или подтвердить информацию, которая была упомянута в предложении.