YOU SAID:

if a cat and a mouse end up in a fight the cat will win

INTO JAPANESE

猫とネズミが戦ったら猫が勝つ

BACK INTO ENGLISH

If a cat and a mouse fight, the cat wins

INTO JAPANESE

猫とネズミが戦ったら猫が勝つ

BACK INTO ENGLISH

If a cat and a mouse fight, the cat wins