Bonjour Alexandra,

This is your third question recently, based upon a past tense.

Perhaps you would benefit from an exercise just on this aspect of French grammar.

I have included a link below which may help you to understand. Why not study the lesson and then post again having done so, with any further points of concern?

https://www.lawlessfrench.com/grammar/verb-tense/

Bonne continuation.

Jim

Alexandra, this is a specific event being described and it has a clear ‘starting’ point (no pun intended). It is not just background briefing or narrative, it is a vital piece of the story being told.

As Jim notes, it is worth reading and viewing different presentations on imparfait versus passé composé, as it is a difficult area for non-native speakers to acquire. The rules are one thing, but it is essential to develop a ‘feel’ for the different uses, and this requires a lot of exposure.

Below is a link to one of the best practical discussions I have found. 

There are also many very good YouTube videos on the topic by a range of good native speaker French language teachers (Alexa, Pierre, Pascal, Dylane, Johan, Hugo are some names to add to your search for generally good material).

Start with simpler ones in English, then some of those in relatively easy to follow French (Hugo Cotton).

To start, it may help to know that in everyday speech, passé composé is more commonly used to talk about things that have happened, you have done, than imparfait, although that doesn’t make the latter uncommon. The verb ‘être’ is however mostly used in imparfait, but not always.

https://www.frenchtoday.com/blog/french-verb-conjugation/passe-compose-versus-imparfait/