I struggled to translate this because in English, we would say 'we have lived together for 60 years', but we haven't learned the past yet so I assumed I would be marked wrong for doing so. I wrote 'we lived together from 60 years' and was marked correct, but then found that the correct translation they suggest utilized the past tense. Bit confusing, because in the past I have translated things to make them sound proper in English, using the past tense, and been marked wrong.
The simple present tense is a lot more versatile in Italian than in English.
For a sentence where in English you use the present perfect tense (unspecified time up to now, e.g. "I have lived") or present continuous tense (e.g. "we are going"), an Italian would use the simple present (e.g. "andiamo", "we go", rather than "stiamo andando", "we are going").
Check out http://italian.about.com/od/verbs/a/italian-verbs-present-tense.htm for an overview. =)
Answering yours, CTrinity's, and jbrener's question all at the same time here, I believe.
As I see it, we use "da" here because the past tense is implied through "da", while "per" would mean present tense ("We live together for sixty years"). If "da" is not actually past tense in Italian, then the past tense comes through in the English translation:
"We live together from sixty years" sounds weird in English "We have lived together for sixty years" sounds better and is the past-tense equivalent of the above sentence.
Hope that helps!
I disagree. See Greg's comment below. This is a legitimate Italian sentence. duoLingo is teaching us the Italian way of saying this. The only other option is to leave out this kind of sentence all together until we learn past tense. I would rather learn it now .. it seems appropriate in this section. Sure, I lose my heart the first time because I don't understand that it needs to be translated to English in the past tense, but after that I am familiar with the Italian phrase and how to comfortably say it in English.
It's more a continuous tense—"we've lived" suggests continuous activity from the past that persists into the present. In English it sounds more past (though the operative word is "we HAVE [present] lived together" but in Romance languages this time-concept is usually expressed in the present like this.
So in isolation "viviamo insieme" means "we are living together." But as soon as you add "da" you're talking continuous. Hope that helps.