All of that will work in his favor so I hope that your father does well!
Dear,
Yes the doctor told me that its at low stage only. Before this my father's health was very very good, means he never had any issue with his health in past. Even he never had a single pain killer in his 56 yrs of life. No other issue he is having
Did they tell him what "stage" the cancer is?
There are so many variables - his health before the cancer, the size, the aggressiveness, and how he is responding to treatment (and everybody is different even though it may be the same treatment for the same tumor) so that question is just not one that can be answered.
As for precautions, he will need to be monitored via scans and keep an eye out for any change in symptoms. Keep a healthy diet and outlook and do his best. I hope he does well.