"Eine Katze hat neun Leben."
Übersetzung:A cat has nine lives.
It's not wrong, but it's the emphatic form of the sentence. To my knowledge there's no equivalent form in German. Most of the time the emphatic form is only used in questions and negative sentences (e.g. "Does a cat have.nine lives?" and "A cat doesn't have nine lives"), but otherwise the emphatic form indicates strong emotion and/or disagreement.
A: A cat has nine lives.
B: I heard a cat actually has seven lives.
A: No, a cat DOES have nine lives!
Perhaps 'Eine Katze hat doch neun Leben"?
But yeah, 'does' is only really used like that to contradict a previous statement or piece of information, especially a negation.
Edit: Or when introducing a piece of information that supports an opposing perspective, as in:
"How did that cat survive a thirty story fall?!"
"Well, a cat does have nine lives."
You are confusing live and life... the cat lives (verb), but she has nine lifes (noun).