On the original British version (VHS) there are no subtitles.
The movie is based on a novella by Graham Greene and he wrote most of the script, except for the famous cuckoo clock line by Welles and perhaps a few lines by Reed.
Regarding Nelly Arno as Kurtz' mother, the only scene that I think could be her was when Kurtz was playing violin at the restaurant - the corpulent woman who was eating soup as he played. Other than that she may have been cut?
A few hors d'oeuvres:
The largest deletion in the American cut was an exchange of dialogue between Martins and Kurtz outside Lime's building, just after Martins asks about Anna's identity.
The scene in which Lime jauntily walks across the amusement park to meet Martins at the base of the Great Wheel is cut by about seven seconds. And the unforgettable final sequence -- with Martins waiting for Anna as she slowly walks up the avenue -- is a full 35 seconds shorter than the British version.
In several instances, scenes with characters speaking German were trimmed. A few seconds of the play in which Anna appears was removed, and at least three shots of Anna's German-speaking landlady were substantially shortened.
It gives a sense of a stranger in a strange land. I think it was a good effect.
Selznick proposed Cary Grant star as Martins, opposite Noel Coward as Lime and later, Jimmy Stewart as Martins and Robert Mitchum as Lime. Reed wanted Welles.
Also, Welles was not in Vienna for the final shooting and so Reed's fingers are what we see coming through the manhole.