YOU SAID:

Nick doesn't know what he's talking about

INTO JAPANESE

ニックは彼が何について話している知らない

BACK INTO ENGLISH

Nick is talking about something he don't know

INTO JAPANESE

ニックは彼が知らない何かについて話しています。

BACK INTO ENGLISH

Nick is talking about something he doesn't know.

INTO JAPANESE

ニックは、彼 doesn't 知っている何かについて話しています。

BACK INTO ENGLISH

Nick, he is talking about doesn't know anything.

INTO JAPANESE

ニックは、彼は話しているについては何も知りません。

BACK INTO ENGLISH

I don't know anything about Nick, he is talking.

INTO JAPANESE

ニックについて何も知らない、彼は話しています。

BACK INTO ENGLISH

I don't know anything about Nick, he is talking.