Olá, @nmarquet. Sorry, I missed this topic before!
So, you might have already seen this Learning Note on the pretérito imperfeito (imperfect past / past continuous): Past Continuous Tense | Practice Portuguese
But this other forum post might help you understand more clearly the differences in use between that tense and the pretérito perfeito (simple past): Era uma noite escura e tempestuosa - Portuguese Questions - Practice Portuguese → The post is on a thread dedicated to creative writing, but the comment also reflects how the tenses are used in the real world.
Let me know if you have any follow-up questions after going through those 