YOU SAID:

Isn't this party great?

INTO JAPANESE

このパーティーは素晴らしいではありませんか。

BACK INTO ENGLISH

This party was great or not.

INTO JAPANESE

このパーティーは素晴らしかったですか。

BACK INTO ENGLISH

This party was great.

INTO JAPANESE

この党は偉大だった。

BACK INTO ENGLISH

This party was great.