помогите пожалуйста разобраться с функциями инфинитива

1. It was nice to be speaking English again.
2.His intention was to get into parliament.
4. They must leave at noon.
5. Dan learned to read when he was five.
6. At times, the young man played the piano loudly enough to burst our eardrums.
7. We didn't have enough time to stay at the seaside for more than five days.
8. She nervously put her hand to her mouth as if to stop coughing.

инфинитив - это глагол в неопределенной форме, в английском он с частицей -to

1-was- прошедшее время глагола « to be» единственного числа.2-was см.1 4-они должны уйти к вечеру. Must- пользуется на все числа( единственное/ множественное) без изменения.5-past continues V+ed...when...was/were.6-V+ed— regular verb.7-