Mama

Mama is a 1990 Chinese film directed by Zhang Yuan. Zhang Yuan's directorial debut, Mama is now considered a seminal film in the history of Chinese independent cinema, and by extension, as a pioneering film of the Sixth Generation of which Zhang is a member. Shot on a very low budget within Zhang Yuan's apartment, Mama follows the story of a mother and her mentally challenged adult son.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.