This makes me think of a relationship that is in need of a boost.
Some critique:
We've heard the bird sing
We've saw those stars hang,
^
I appreciate your first language may not be English, so I just want to highlight that 'Hang' doesn't rhyme with 'Sing' Maybe if you changed the first line to this: The sweet birds sang
We've been to paradise before
Played the sand at the shore.
We've been at the top
Now down in one snap
^
Maybe a typo on the word, 'snap' did you mean stop?
Our dreams collapsed
Everything screwed up.
^
Not sure if you are trying to rhyme here?
The opportunity knocked
Then we opened the locks
^
good
Someone punched it closed
Little by little our hearts decomposed.
^
good rhyme, but the flow seems slightly off, maybe try, 'slowly our hearts decomposed'
Our eyesight was blinded
Arms and legs were banded
^
Here the rhyme is slightly off - it could be left, but it is a little distracting.
Chasing our dreams in the dark
We'll be needing some sparks.
^
Very good flow, rhyme and simile.