Person (65 years old) suffers from sever cough and difficult in breath. Doctors said its pulmonary fibrosis? Please what's drug or treatment to him?

Very little. There is no therapy for pulmonary fibrosis. Symptomatic relief may be helped with oxygen , Imuran (azathioprine) and possible steroids, progressive dis may be treated with lung transplant.
Depends on the cause. There is no good treatment to reverse pulmonary fibrosis but the progression may be thwarted if one knows the trigger mechanism. I presume that this person is under the care of a board certified pulmonologist who may prescribe oxygen for the condition.