Career
Strømsgodset
He got his breakthrough in the 2014 season, when he gradually worked his way into the first team, featuring in 26 of the 30 league matches. In the 2015 season, he became the top scorer for his club, which ended 2nd in 2015 Tippeligaen. Hannover 96
Fossum signed a contract until June 2020 with Hannover 96 on 23 December 2015, in a deal worth 20 million NOK.