Searching ancestors Berg

I am searching for ancestors, my granddads brother who probably went to America and it might have been in 1931 according to my aunt. His name was Halfdan Frithdjoff Petersen Berg, born in Halden of Ostfold on the 3. Dec. 1896. Cristening 14. Feb 1897. His fathers name was Peter Fredriksen Berg, born 1869, later changed to Petter Berg. His mothers name was Helga, born in Glemminge, Freddrikstad Norway in 1872. He had several siblings among these my grandfather Rolf Markus Petersen Berg who had a twin called Eugene Gustav petersen Berg...... They had 3 sisters and a younger brother who died only 24 years of age. All this information I can find in the church books in Norway. But when it comes to information about Halfdan Frithdjoff Petersen Berg after his birth is hard to get to. I have found some people named Petersen Berg in America, but haven't been able to get the phome number or anything else. And i guess there are common names. One Edel (Edelhardt) Petersen Berg I found and one Elisabeth i think it was.... There are no information about where he went and the Salvation army was looking for him with no luck apperantly many years ago, according to my dad. Anyone has any ideas??? [:)] It would be highly appriciated