YOU SAID:
C# is a useful language, that I don't know
INTO JAPANESE
C#は私が知らない便利な言語です
BACK INTO ENGLISH
C# is a useful language that I don't know
INTO JAPANESE
C#は私が知らない便利な言語です
BACK INTO ENGLISH
C# is a useful language that I don't know
That didn't even make that much sense in English.