YOU SAID:

The jello will not stiffen

INTO JAPANESE

ゼリーが固くないです。

BACK INTO ENGLISH

Jelly is not stiff.

INTO JAPANESE

ゼリーは硬いです。

BACK INTO ENGLISH

Jelly is hard.

INTO JAPANESE

ゼリーは難しいです。

BACK INTO ENGLISH

Hard jelly.

INTO JAPANESE

ハードのゼリー。

BACK INTO ENGLISH

Hard jelly.