YOU SAID:
my cat is extremely dumb
INTO JAPANESE
私の猫はとても頭が悪い
BACK INTO ENGLISH
my cat is so dumb
INTO JAPANESE
私の猫はとても愚かです
BACK INTO ENGLISH
my cat is so stupid
INTO JAPANESE
私の猫はとても愚かです
BACK INTO ENGLISH
my cat is so stupid
That didn't even make that much sense in English.