Career
A Flensburg native, Christiansen started playing football with local sides SV Adelby and Flensburg 08. In 2010, at the age of 13, he moved to the youth ranks of Holstein Kiel where he stayed only one year though. He joined the football academy of Hansa Rostock, this included attending a private school.
Subsequently he made his way through Rostock"s youth teams and eventually got promoted to the first team, playing then in 3.
Liga. He debuted on 29 March 2014 in home match against Stuttgarter Kickers, playing 80 minutes as a starter. In the following Christiansen became a regular and attracted the attention of several topand second-flight clubs.
In the next winter break, 2014-2015, Rostock faced massive financial difficulties and had to acquire income through selling players. Christiansen moved to 2.
Bundesliga club Football Club Ingolstadt for a transfer fee of believed to be €500,000 and signed a three-and-a-half-year contract until 2018.
Christiansen is at the moment the captain of the Germany U20, having earned six caps up to now. Previously he also was capped for the U19 and U17 teams.