After studying English and Romance literature under Werner Krauss and Hans Mayer at the Karl Marx University in Leipzig, he became a freelance translator from English, French and Spanish (Calderón, Cervantes, Neruda, Buero Vallejo and others), an interpreter (in Prague and Moscow, and elsewhere) and a writer.
In 1972 he became a member of the PEN Center of East Germany and shortly afterwards was elected to the presidency.
Gabriele Wohmann remarked that "Fries's work belied the stereotype of the technically awkward, thematically constrained, stylistically cautious and staidly narrational East German writer."
In 1996 it was revealed that he had worked as an informant for the Ministry for State Security (from 1972 to 1985 under the codename "Pedro Hagen").
Fries lived in Petershagen, Berlin and contributed articles to several daily newspapers until his death in 2014.