Не уверен, но постараюсь
1. I tought you were playing with your little sister
You said you would play with your little sister. And i was sure you played with her.
2. I tought you were playing chess.
You said you would play chess. And I was sure you played chess.
3. I tought you were doing your (не разглядел слово)
You said you would do your(слово).And I was sure you did it