"We are here and we are a mirror."
Translation:Nós estamos aqui e nós somos um espelho.
Not more than in English ;). Duo seems to try be funny and to show the different translations of to be:
Estar (transitory states, as location, verbs in continuous tenses etc) Ser (permanent states, as name, nationality and so on).
Maybe it would be easier to get:
I am (eu sou): American (americano/americana), white (branco/branca), a human being (um ser humano), an engineer (um engenheiro/uma engenheira)
I am (eu estou): In a hurry (com pressa), in the yard (no quintal), eating (comendo)
There are lots of exceptions to drive you mad, of course :)
For example, some states can be both, with a slight change of meaning:
I am a happy person (sou uma pessoa feliz). I am happy because I have a winner ticket (estou feliz porque tenho um bilhete premiado).
Some just translate completely different: I am 30 years old = eu TENHO 30 anos de idade.