This is Hel (2016)

"The truth is very simple."

Jack, an unappreciated American writer in his sixties, comes to the off-season peninsula of Hel in the north of Poland and isolates himself to write a script. He meets Kail, a local who earns money by making lie-detector tests. Jack doesn't find any inspiration until some tourists mysteriously disappear - one of them found dead with his tongue cut off. Kail, persuaded by his friend Mila that Jack is the murderer, begins an investigation. The truth turns out to be more twisted when he discovers that Jack is writing about him.