I am 25 years old male and my partner is 26. When I try to intercourse, I am unable to get erection. I am unable to satisfy my partner because of that. What may be the reason? What should I do to get proper erection of penis. Is it good to use viagra? Please help.

You should see your doctor. There are many medical reasons (some serious) that can cause this. You should not be taking medication till you know a reason.

As was mentioned, you need to see a doctor. They have to examine you to examine you before they can diagnose much less treat it appropriately.

Go see a doctor my young friend, and get the facts, and proper solutions to this problem. Has this happened before?