YOU SAID:

My dog ate my cat but he was already a cat.

INTO JAPANESE

私の犬が私の猫を食べましたが、彼はすでに猫。

BACK INTO ENGLISH

My dog ate my cat, but he is already the cat.

INTO JAPANESE

私の犬は私の猫を食べたが、彼はすでに猫。

BACK INTO ENGLISH

My dog ate my cat, but he is already the cat.