YOU SAID:

This is really stupid and I don't understand.

INTO JAPANESE

これは本当にばかげていて、わかりません。

BACK INTO ENGLISH

This is really ridiculous and I do not know.

INTO JAPANESE

これは本当にばかげていると私は知りません。

BACK INTO ENGLISH

I do not know that this is really ridiculous.

INTO JAPANESE

私はこれが本当にばかげていることを知りません。

BACK INTO ENGLISH

I do not know that this is really ridiculous.