After both of her parents died, she worked as a translator for Polish and Russian, and as a writer for the Deutsche Presse-Korrespondenz in Hannover, the Ullstein-Verlag, and the Scherl-Verlag.

Moja began taking acting lessons with Emmanuel Reicher and Frida Richard and made her debut in 1913 at the Lessing Theater in Berlin.

Some of her early film appearances include The Path of Tears (1916), The Oath of Renate Rabenau (1917), The Stranger (1917), and The Enchanted Castle (1918).

Her first production was Wondrous is the Fairy Tale of Love (1918) with Ernst Hofmann, for which critics praised her acting.

In the 1920s, Moja starred in films such as Countess Walewska (1920), directed by Otto Rippert, What a Girl (1920), Felicitas Grolandin (1923), Department Store Princess (1926), U-9 Weddigen (1927), and The Carousel of Death (1928).