YOU SAID:

I really don't know how to tell you this, but you're really stupid.

INTO JAPANESE

どうやって伝えたらいいのかわからないけど、あなたは本当にバカね。

BACK INTO ENGLISH

I don't know how to tell you, but you are really stupid.

INTO JAPANESE

どう言っていいのかわかりませんが、あなたは本当にバカです。

BACK INTO ENGLISH

I don't know what to say, but you are really stupid.

INTO JAPANESE

何を言いたいのかわからないが、あなたは本当にバカだ。

BACK INTO ENGLISH

I don't know what you mean, but you are really stupid.

INTO JAPANESE

何を言っているのか分からないけど、君は本当にバカだ。

BACK INTO ENGLISH

I don't know what you're talking about, but you're really stupid.

INTO JAPANESE

何を言っているのかわからないが、あなたは本当にバカだ。

BACK INTO ENGLISH

I don't know what you're talking about, but you're really stupid.