"nous sommes quitte" is a standard expression you use when you leveled the field with someone, having giving him something you owed him (or having received from him, something he owed you). The meaning is "neither of us owes something to the other anymore"
It can be either a positive thing (a meal for instance: you went at his house for lunch last month, he went at yours for dinner yesterday, so you're no more 'in debt')
It can well be a negative thing (for instance after trading blows or bad tricks)
Sommes-nous .... means 'are we ...' in French.
"Nous sommes" means "we are" in English.
"sommes-nous ..." means 'are we ..' in French.
Nous sommes .... depuis .... means "we are ... since ..." Ex: nous sommes boulangers depuis 1980 (we are bakers since 1980)
"(ne) sommes-nous pas" means "aren't we ..." in English. This is a question form from "nous ne sommes pas ..." (we are not ...)
"Nous sommes ici" means "we are here" in French.
"sommes" is a form of the verb "être", to be."nous sommes" = we are.
(il/elle) nous a quitté - (he/she) has left us (it could mean that the person in question has just died)
It means 'We are'
You can say "Nous sommes arrivés" in French to mean "We've Arrived."
"we are" tanslates as -- 'nous sommes' : 'nous' meaning we and 'sommes' meaning are
"(ne sommes-nous pas ..." means "aren't we..." - Nothing special about lovers in that expression.