Bergstein was born in Copenhagen on 7 July 1941.[1] He joined the Royal Danish Air Force in 1971.[1] He was promoted to the rank of captain in 1975 and became a major in 1980.[1]
Bergstein was an advisor at the Ministry of Defense between 1988 and 1993.[2] He was a national secretary of the Center Democrats.[3] In 1993 he was appointed minister of higher education and science for the party in the cabinet led by Poul Nyrup Rasmussen.[3] Bergstein was dismissed from the post in 1994 and he resigned from the Center Democrats following his dismissal.[3] He then taught at the Defense Academy.[3] He served as a military expert on the Danish television channels during the Gulf War in 1991.[4] In 1995 he joined the Conservative People's Party.[3] He served as a military attaché of Denmark in Sweden and Finland from 1995 to 1999.[2] He was a section chief at the Defense Academy until 2001 when he retired with the rank lieutenant colonel.[2] In 2007 Bergstein was elected as the head of Copenhagen branch of the Conservative People's Party.[3]