Lossow, born to a master tailor, began his artistic training at the age of 15 under sculptor Heinrich Freese. He assisted Freese with several projects, including the reliefs of the Ostertorwache. His skills soon led him to the studio of sculptor Ernst Mayer in Munich, where he contributed to a relief on the Siegestor.
Before his sojourn to Rome, Lossow had the fortune of meeting Ludwig Schwanthaler, a fellow artist. On his return in 1834, he became Schwanthaler's assistant. Within the creative confines of Schwanthaler's workshop, eleven statues were born for the west and east facades of the Glyptothek, featuring notable artists such as Antonio Canova, John Gibson, Ludwig Schwanthaler, and Bertel Thorvaldsen.
Lossow's talents were not limited to Munich and Rome. In Bremen, he crafted several tombstones, the most renowned of which was commissioned in 1847 by the family of shipbuilder and shipowner Johann Lange. In 1843, Lossow was granted honorary membership of the Bremen Art Association, and he exhibited his work at the Bremen Art Hall in 1845 and 1852.
Lossow's life journey came to an end in 1874, in Munich.