After watching the film Lady in the Water (2006), József Gallai decided to pursue filmmaking and began writing screenplays and stories. Between 2009 and 2012, he mainly participated in amateur films of various genres.

In 2014, he wrote the screenplay and co-directed Hungary's first feature-length found-footage horror film, Bodom (2014). That same year, the film opened the Bram Stoker International Film Festival in Whitby, UK, and also garnered numerous nominations at film festivals, including the 30 Dies Festival in Andorra, the Golden Rake Award for Indie Horror and the New York Scary Film Awards in the USA, and the Amazon Horror Awards in Brazil.

In 2015, Bodom made the final competition at the Full Moon Horror & Fantasy Film Festival in Romania, competing with such award-winning films as The Puppy (2014), Horsehead (2014), and Reality (2014).

In early 2016, his next horror film, The Moth (2016), was completed, and it placed 4th in the Best Feature Film category at the International Horror Hotel in Cleveland, Ohio. The film was called "thought-provoking and blood-chilling" by Found Footage Fiction and "a contender for a new niche in horror" by Horror Habit. According to Horror Asylum, The Moth is "an unusual experience, some moments of which remind the author of David Lynch's Inland Empire (2006)."