YOU SAID:

my dog ate some muffins while my cat had a shower

INTO JAPANESE

私の猫がシャワーを浴びている間に私の犬はマフィンを食べ

BACK INTO ENGLISH

My dog ate muffins while my cat was taking a shower

INTO JAPANESE

私の猫がシャワーを浴びている間に私の犬はマフィンを食った

BACK INTO ENGLISH

My dog ate a muffin while my cat was taking a shower.

INTO JAPANESE

私の犬は、私の猫がシャワーを浴びている間にマフィンを食びました。

BACK INTO ENGLISH

My dog ate a muffin while my cat was taking a shower.