I want a cigarrette, but I need to let smoking: po qué dice duolingo estar mal????? To let = dejar
dejar also means "to stop"
"Let" se usa para permitir o dejar hacer algo a alguien.
I want a cigarette, but I need to give it up
"]I want a cigarette but need to stop smoking" should also be accepted. You don't need the extra"I".