Yeah, that's fine I think, but I thought I'd take this opportunity to point out that the title of this lesson (Past Perfect) shouldn't be understood as being an exact equivalent to our (English) Past Perfect. It just means Perfective verbs in the Past tense, as far as I'm aware.
Usually the Past Simple would be best to translate them to, because the concept simply requires a finished action in the past (in English we only use Past Perfect to contrast two actions in the past so that we know which occurred first, it's a very specific tense).
the name of the lesson is misleading. It should be something more like "perfective verbs in past"
They can be translated into past perfect, present perfect or past simple depending on context.
Polish used to have equivalent of Past Perfect, but it's not used any more, only by some old people or when styling the sentence to feel old-fashioned. And it is definitely not taught in this course.
Yes that is it.
You ony use it for stylistic purpose, so unless you are planning on becoming translator or writer you would not need it.