Using the compound tense (Le Passé Composé) on its own or with the imperfect tense (L'Imparfait)

The main difficulty when talking about the past in French is to know when to use L'Imparfait (Indicatif) or Le Passé Composé (Indicatif). 
In this lesson, we're going to look at how to use Le Passé Composé (Indicatif) on its own, as well as combined with L'Imparfait (Indicatif).

(Reminder of the different usages for L'Imparfait (Indicatif): expressing continuing actions , habits or repeated actions Expressing past habits or repeated actions with the imperfect tense in French (L'Imparfait), or for descriptions and past states Expressing opinions and describing with the imperfect tense in French (L'Imparfait))

When to Le Passé Composé (Indicatif) with L'Imparfait (Indicatif) or on its own in French  

Look at these examples in Le Passé Composé (Indicatif):

 
Now look at these sentences where both Le Passé Composé (Indicatif) and L'Imparfait (Indicatif) are used:

BONUS:
Let's look at these contrasting examples and their nuances:

-> Here, I'm stating that it was cold during the night, insisting on the fact that this situation was ongoing then, describing the situation.

->Here, I'm referring to a past action that has a clear timeframe in the past, insisting on it being a single, whole past event.