Past perfect is a tense; perfective is an aspect, and this group of exercises relates to the past tense of perfective verbs.
I take your point that the title for this group of exercises is actually misleading.
"powiedzieć" is the perfective aspect version of "mówić".
Well, my "goto" resource is Wiktionary.
You probably don't need help with "nie", but let's look at "powiedziałem".
https://en.wiktionary.org/wiki/powiedzia%C5%82em tells you that "powiedziałem" is "first-person singular masculine past of powiedzieć" and https://en.wiktionary.org/wiki/powiedzie%C4%87 then gives the full conjugation, relationship to another verb "mówić", and so on.
Repeat for "tego".