YOU SAID:

I told you, I haven't done this before.

INTO JAPANESE

言っただろう、こんなことはしたことがない。

BACK INTO ENGLISH

I told you, I've never done this before.

INTO JAPANESE

言っただろ、こんなことは初めてだ。

BACK INTO ENGLISH

I told you, I've never seen anything like it.

INTO JAPANESE

言っただろこんなの見たことがない

BACK INTO ENGLISH

I told you, I've never seen anything like it.