"Nie myślę, że ten pomysł jest gorszy."

Translation: I do not think that this idea is worse.

[Jack.Elliot]

i am not thinking that this idea is worse

[BronwynYoung]

Could someone please tell me why we don't use genitive here? (Negation)

[Arnoldpitt]

"That" is more often omitted in English

[Jellei]

Possibly, but it's safer to have some equivalent of "że" in the main translation. You may of course omit it, it will be accepted.

[JokerFox17]

I dont think that this idea is the worst

[Jellei]

"the worst" is "najgorszy", not "gorszy".