"To all your friends, you're delirious
So consumed in all your doom
Trying hard to fill the emptiness
The piece is gone and the puzzle undone
That's the way it is"

Christina Aguilera-Beautiful

My question is if i can say

"Trying hard to fill the emptiness, the piece is gone."

Please help me understand.

Thank you.
It's a song. It's poetry.
Poets take liberties with language. They can bend (or break) the rules to create certain emotional effects.
That is called "poetic license".

You would not carry on normal conversations using poetic language. Your friends would think you were very strange indeed.

Jigsaw Puzzle -- Note that the puzzle consists of many pieces. This puzzle is unfinished (undone).

The song writer is comparing her life to an unfinished jigsaw puzzle.

She is trying with great effort to complete the puzzle. (Trying ... to fill the emptiness.)

There is a piece missing from the puzzle. (The piece is gone.)

So the puzzle is unfinished. (The puzzle is undone.)