YOU SAID:

Why did I do that - it was the biggest mistake I have ever made

INTO JAPANESE

なぜ私はそれをやったのですか？それは私が今までに作った最大のミスでした

BACK INTO ENGLISH

Why did I do that? That was the biggest mistake I made ever

INTO JAPANESE

なぜ私はそれをしましたか？それが私が今までに作った最大のミスでした

BACK INTO ENGLISH

Why did I do that? That was the biggest mistake I made ever