That was an excellent answer. I fully understand the concept of Perfective and Imperfective. My problem was the meaning of these two words but with the examples you provided the meaning was clarified.
As I understand skazat' is used with Dative: ona skazala nam, chto ... = She told us that ...
Pogovorit' is synonym of having a dialogue with someone and it is used with the Preposition: "c" + Instumental e.g. Я вчера поговорил с Петром
Pravil'no?