 A free agent, Geertsen received a number of offers from clubs in Denmark and Norway, including Bodø/Glimt and Tromsø, but he also had a trial at Nykøbing FC, who he ended up not signing with due to its long distance to Copenhagen.In March 2018, he signed with Danish third tier club Hillerød, making his first start only days after joining, in a 2–2 away draw against VSK Aarhus.Geertsen signed a contract with Lyngby Boldklub from the Danish 1st Division in July 2018 after having trained with their first team, marking a return to the club from his youth.