Прошедшее время группы "continuous" используется для обозначения действия, имеющего отношение к определённому моменту в прошлом или для описания обстановки.
Прошедшее время группы "continuous" образуется при помощи глагола
"to be" = "was/ were" + "ing" :
What were you doing at five yesterday? = Что вы делали в пять часов вчера?
They were having dinner when I came = Когда я вошёл, они обедали.
I was waiting for you at five o'clock yesterday = Я ждал вас в 10 часов вчера.
What were you doing when I came in? = Что вы делали, когда я вошёл?
I was writing to my sister at seven o'clock in the morning = В семь часов вечера я писал письмо сестре.
My son was doing his lessons when his friend came to see him = Мой сын готовил уроки, когда пришёл его друг.
We went out. There were a lot of people in the street. Some of them were hurrying home from work. A boy was walking on the other side of the street. Some other children were playing near their house. An old woman was walking to the park with a little girl. I went to the park, too, and sat down at a bench.