Severe abdominal pain in my friend today. If it passes in 1/2 hour, that means it was just a gas bubble?

Probably. So long as it doesn't recur. Severe pain that is recurrent could be any number of things and should be evaluated by a physician.
Maybe. Certainly could be gas pain, but can't tell here. Could be other stuff too. Don't know your friend, age, sex, history, etc, didn't examine your friend. Certainly if fever, recurrentt pain, nausea, vomiting, shking chills, change in bowel habit, urine complaints, blood loss vfrom anywhere, etc., needs to get seen by md pronto.