YOU SAID:

the party is at 9 o clock don't be late

INTO JAPANESE

パーティーは9時に遅れない

BACK INTO ENGLISH

The party is not to be late at nine.

INTO JAPANESE

パーティーは9時に遅れはない。

BACK INTO ENGLISH

The party is not late at nine.

INTO JAPANESE

パーティーは9時に遅くはない。

BACK INTO ENGLISH

The party is not late at nine.