Re: Bulgarian: Past Perfect and aspect
With the auxiliary you are using:
"сметнали" expresses something that happened once (before a past moment).
"Смятали" expresses that the two guys thоught so for a while (before a past moment) (though in your case it's the negative of the tense - they didn't find guavas remarkable).
Your first sentence is indeed wrong. "Бяхме сметнали" as an action that only happened once (we decided so at a certain moment) excludes the use of "някога".
"Бях" will only go with "сметнал" in an "If" phrase: "Ако бях сметнал, че е неподходящо, нямаше да дойда".
BUT... since "смятам" is a verb that expresses an opinion, when you say "бях сметнал", it sounds like "I'm thinking that it's wrong" or "I'm wanting this". It doesn't fit so well for certain tenses. We would say "Ако смятах, че не е неподходящо, нямаше да дойда".
Kanes is right about you referring to yourself by name. In case you are Ivan, you could say :
До онзи момент (the moment you changed your mind about guavas) нито аз, нито Павел намирахме нещо забележително в гуавите.
До онзи момент аз и Павел никога не бяхме мислили, че гуавите са забележителни.
I could not name any tenses, sorry about that!
I am spared by mercy, a child of His grace