I learned the following equivalences
Unlearn those. German tenses do not map to English tenses that way. German has no perfect aspect. (And neither a continous aspect.)
German tenses follow a simple orthogonal scheme. There's all the simple tenses that do not employ the Partizip II. Those are for the non-past. And there's all the perfect tenses that do employ the Partizip II. Those are for the past.
So you cannot talk about the past without using the Partizip II and the Perfekt auxiliary.
If you use Präteritum instead, you don't talk about the past but you tell a story. And that Präteritum is the present inside the story universe. As most stories are about the past, this is sometimes at least understandable. But consider:
- Das Planet-Express-Raumschiff stürzte auf die Straße, weil Bender die L-Einheit verbogen hatte.
This isn't the past. It's the year 3000! And the present inside this story universe is marked with Präteritum while the past inside it is marked with Plusquamperfekt.
Okay. Here's the full scheme.
- Präsens / Perfekt — facts
- Präteritum / Plusquamperfekt — narration
- Futur I / Futur II — assumptions
- Konjunktiv I / Konjunktiv I Perfekt — hearsay
- Konjunktiv II / Konjunktiv II Perfekt — counterfacts
- Konjunktiv I Futur I / Konjunktiv I Futur II — hearsay assumptions
- Konjunktiv II Futur I / Konjunktiv II Futur II — replacement for Konjunktiv II / Konjunktiv II Perfekt
Futur II is a perfect tense. Those hearsay assumptions are seldom used and Konjunktiv II Futur I / Konjunktiv II Futur II you have probably learned about as the würden-Konjunktiv II.
As you can see, the simple/perfect pairs differ in the intent of speech. But you always have that simple tense for the present, and that perfect tense for the past.
On top of that scheme, Northerners use Präteritum in place of Perfekt for the auxiliaries, the modals and a few very common verbs. Not more than a handful. The more southern the speaker is from, the less verbs are mangled that way. In Austria they only use sein that way. In Switzerland not even that.