This question has probably been asked many times, so I apologize in advance. After seeing many examples of past perfect and past perfect progressive, I still can't figure out when and how exactly to use it. Some people say it emphasizes the process of an action expressed via past perfect, some people that it puts greater distance between actions of past perfect and past simple and some that it shouldn't be used when it's unnecessary. But I often see it used when having not used it would have provided the same clear and consistent picture. I would be very grateful if someone explained the difference between past simple and past perfect in the examples I will provide below.
I bolded the answers I thought fit better.
After I (had done/did) all of my homework, I was finally free to go outside and play with my friends.
I felt pain in my stomach after I (had just eaten/just ate) a very large breakfast.
(The use of past perfect in sentences with after and before always feels strange to me, because those prepositions already provide the clue to decipher which action happens first, but I would choose past perfect over past simple here)
I have examined the document you (had given/gave) me and...
I found this example while browsing Stack Exchange and people said that "gave" sounded better. But there is no answer as to why, and as I see it, the action of giving happened before the action of examining.
I (had not spoken/didn't speak) any English in my childhood and adolescence, but I started studying it at university.
I (had been/was) walking down the street when I suddenly saw a $100 banknote someone (had/-) conveniently lost for me. Before choosing what to do with my unexpected windfall, I (had/-) phoned my friends to share my hesitation if spending that money was the right thing to do.
(Would past perfect progressive in "had been walking" be possible? Something like "I had been walking down the street for hours when I suddenly saw him waiting for me"?)
I (had/-) lived on X street before finally deciding to move out, but my parents were not happy to hear about my decision because they (had/-) always wanted me close by.
(I want to express that they wanted me close by before I decided to move out)
After they (had/-) finally agreed to my persistent persuasion, I started packing my things up but it wasn't long until I discovered that my father (had/-) sold the whole collection of my CDs. I was angry because I (had-) been listening to them when I (had been/was) young and (had/-) felt depressed.
I can't give you any reasons to why I chose what I chose, just what sounded better to me.