(1) I saw many fireflies when I was a child. 「私が子供の頃、たくさんのホタルを見ました。」 →I didn't see many fireflies when I was a child. →Did you see many fireflies when you were a child?
(2) Rivers in our city are dirty now. 「私たちの市の川は今は汚いです。」 →Rivers in our city aren't dirty now. →Are rivers in our city dirty now?
(3) They cooked dinner for thier mother yesterday. 「彼らは昨日お母さんのために夕飯を作りました。」 →They didn't cook dinner for their mother yesterday.
(4) I enjoy playing video games. 「私はテレビゲームを楽しみます。」 →I don't enjoy playing video games. →Do you enjoy playing video games?
(5) She gets up at six thirty every morning.
→She doesn't get up at six thirty every morning. →Does she get up at six thirty every morning?