Complex sentence: From 1806 to late February 1808 Skibsted was a teacher at the Naval Cadet Academy, part of the time on HDMS Prins Christian Frederik which ship-of-the-line was then acting as a cadet training ship.
Split into simpler sentences: From 1806 to late February 1808 Skibsted was an instructor at the Naval Cadet Academy. He spent part of his time on HDMS Prins Christian Frederik, a ship-of-the-line that was then serving also as a cadet training ship.