In 2017, at his new weight class, he boxed at the European U-22 Championships in Romania, but lost his second fight to former European Youth champion Oleksandr Khyzhniak. He decisioned two fighters before losing to two-time Olympian Zoltán Harcsa in the quarterfinals of the European Championships in Ukraine. This qualified him for the World Championships in Hamburg at the age of 19; he exited with another second-round loss to Oleksandr Khyzhniak. After winning a tournament in Budapest in October 2017, Csemez was involved in a serious car accident that broke two of his cervical vertebrae and kept him out of the ring for eight months. He was knocked out by Andrej Merzlyakov in the first round of the prestigious in Germany in June 2018, then lost by referee stoppage to Nicoleto Grdovič at an international tournament in Slovakia in what was his light heavyweight debut. After this rough return, he then won a gold medal in the middleweight event at the European Union Championships in November, winning all four bouts by unanimous decision. His year ended with his second gold medal at the national championships in December.