He has a student two ears ago,they were in the park last saturday в отрицательную и вопросительную форму

They were in the park last Saturday. They were not in the park last Saturday. Were they in the park last Saturday? He was a student two years ago.  He wasn't a student two years ago. Was he a student two years ago? Я предполагаю так. Если предложение не такое, напишите, я исправлю