I understood nmenez's first question better than his second. I think the confusion comes from the phrase "um pouco duros" which looks a little strange in isolation and would seem better written as "um pouco duro".
You can explain this much better than me, but let me try. The reason it is "duros" and not "duro" is because this word is an adjective and needs to agree in number with with "nós"/"we" which is plural. The phrase "um pouco" is an adverb meaning "a little" or "a bit" and is invariable.
In a sentence like this both the simple past (were) and the present perfect (have been) work. See under "indicative preterite" here:
It's not a stupid question because they are easily confused. They are both versions of the verb "to be" and if it helps at all you can think of them in terms of the corresponding words related to "ser":
- been (past participle) = sido (particípio passado)
- being (present participle) = sendo (gerúndio)
The difference between them is summed up very neatly on this page: http://www.grammar-monster.com/easily_confused/being_been.htm
Use been after the verb to have.
Use being after the verb to be.
The page goes into much more detail and gives several example sentences but I like that summary. Here's a sentence that combines both words: "Whenever I tell people that Duolingo has been helpful, I am being truthful".