Mixed Past Tenses

→ an action that happened at a definite time in the past 

Last year we bought a house 

→ actions that happened immediately one after the other in the past 

Lou took a shower, brushed his teeth, and went to bed.

→ an action that was in progress at a started time in the past.

Yesterday at 4 I was talking to Meg on the phone 

→ two actions that were happening at the same time 

Liz was vacuuming while her sons tidying their room.

→ an action thar was in progress ( longer action) when another action interrupted it.

When I came in, Sue was reading

→ An action that happened in the past 

Before we left, we have booked a hotel room.

→ Complete past action that had visible results in the past 

We felt relieved after they had arrived safely.

→ An action continuing over a period up to a specific time in the past 

Pete had been working as a doctor for 25 years before he retired last year

→ The action of a certain duration that had visible results in the past 

Mark had been studying Spanish for five years before he moved to Toledo.