Olá Felipe. A explicação mais básica é: Passado simples: A ação terminou. Ex: I made a delicious cake last weekend. Passado perfeito: A ação ainda repercute no presente, ou a ação TEM SIDO FEITA com certa frequência, então você precisa do "present perfect". Ex: I´ve made some delicious cakes the last month. É por isso que perguntamos: What have you done lately? - indica uma continuação. Se eu perguntasse: What did you do last night? - a ação teria sido concluída. Há alguns indicativos do uso do Past Simple tais como o uso dos seguintes termos: yesterday ... ago in 1990 the other day last ... Já no Present Perfect é mais frequente o uso de: just already up to now until now / till now ever (not) yet so far lately / recently Bom, espero ter ajudado. Mais não se preocupe logo você entenderá a lógica, quanto mais você praticar mais simples e automático ficará.

This is actually going to be difficult for most English speakers to quantify. The difference between these two conjugations is all about the sequence of a story. When you tell a story in chronological sequence, the simple past tense is straightforward. You say this happened, and then this happened, and then this happened. But when you are in the middle of this sequence, any explanations that go back in time again would be confusing to just keep using the simple past tense. Let's try an example: "So yesterday I went to the mall, and while I was there I ran into Kevin. Kevin told me that his sister was pretty mad at him for losing their tickets." This is a simply story about something that happened in the past. The sequence is easy to follow. Now let's add the next part: "So yesterday I went to the mall, and while I was there I ran into Kevin. Kevin told me that his sister was pretty mad at him for losing their tickets. He dropped them from his pocket when he pulled out his keys." If you stay in the simple past tense, this part sounds a little bit confusing. You can probably figure it out by correcting the storyteller in your head, but you have to think about it. Just saying it like this sounds a little like Kevin told the storyteller that his sister was mad at him for losing the tickets, but then Kevin pulls out his keys and the tickets drop out. The listener could think the storyteller is trying to say that Kevin was mistaken and he had the tickets in his pocket the whole time. Let's change that last sentence to past perfect: "So yesterday I went to the mall, and while I was there I ran into Kevin. Kevin told me that his sister was pretty mad at him for losing their tickets. He had dropped them from his pocket when he pulled out his keys." This now makes it clear that the storyteller is explaining that, at some point before the storyteller spoke to Kevin, Kevin dropped the tickets from his pocket, which is why his sister was mad.

I think you are right. There are many synonyms for the idea that something is finished that can have different implications. You could say: I did my work. My work is finished. I finished all my work. I did most of the work and my friend helped until the project was completed. The exception would be if you were describing a story in the past and needed to indicate that the work had been done before the historical time your story is about. ie, we painted the walls when the the first coat WE HAD PAINTED was fully dry. In common conversation, I doubt you'd have trouble being understood if you opted to use the simple past version. https://www.ego4u.com/en/cram-up/grammar/simpas-pasper