YOU SAID:

I am such a stupid person, why do I do stuff like this

INTO JAPANESE

私はこんなバカな人です、なぜこんなことをするのですか

BACK INTO ENGLISH

I am such a stupid person, why are you doing this

INTO JAPANESE

私はそんな愚かな人です、なぜこれをやっているの

BACK INTO ENGLISH

I am such a foolish person, why are you doing this?

INTO JAPANESE

私はそんな馬鹿な人です、なぜあなたはこれをやっているのですか？

BACK INTO ENGLISH

I am such a foolish person, why are you doing this?