While I waited/ was waiting for the bus yesterday, I saw/was seeing an old friend from school.
was waiting, saw → While I was waiting for the bus yesterday, I saw an old friend from school. (Тривала дія + коротка подія)
2 Leo used to/would like steak but he doesn't anymore.
used to → Leo used to like steak but he doesn't anymore. ("Used to" — для минулих звичок, що більше не актуальні)
3 We were at the beach. The sun used to come down/ was coming down and it would get/ was getting dark.
was coming down, was getting → The sun was coming down and it was getting dark. (Опис двох одночасних тривалих дій у минулому)