While still in school, he financed his first 30-minute film through crowdfunding and took part in the international exchange program Young Nordic Filmmakers at the Nordic Film Days. His short films have been awarded prizes such as the Youth Film Award Schleswig-Holstein and were screened at several regional festivals.

After graduating from high school, he founded the production company Studio Nordlicht GmbH, through which he realized numerous commercial and image films for clients in business, culture, and education. Despite his work in the commercial sector, his passion remained with fictional storytelling—film as an expression of an inner world, an invitation to feel and reflect.

At the end of 2023, Kassun decided to step away from Studio Nordlicht to focus entirely on fictional filmmaking. In 2024, his first feature film, the independent drama Stay a little longer (Bleib doch noch) premiered in Hamburg, In 2025, his short film Leise Feuer premiered at the Filmkunstfest Mecklenburg-Vorpommern. That same year, he was selected for the MOIN Talent Program by MOIN Filmförderung and also took part in the Talent Lab of the renowned children’s and youth film festival Goldener Spatz., as well as the Talent Camp of the Odense International Film Fest in Denmark.

He is currently working on his next short film screenplay.