7 months ago i have infected with flu after that my sense of smell altered so some smell of things will be different after visiting ent doctor he told me that i should use "nasonex" nasal spray for 3 months ..is this drug enough?

Post flu: Altered or even loss of smell can occur as a result of a severe upper respiratory tract infection. Fortunately eventual return of full sense of smell usually occurs but in my experience, it may take weeks or months. I think nasonex type sprays are more worth trying if sinusitis or nasal polyps are present. I don't know if I would extend their use beyond a month otherwise. Discuss with ENT then.