Translation:At the movie theater they are presenting a good program.
"They" is correct. "One" would be wrong here in English, although I can't explain why (native speakers are useless at explanations, I'm afraid!) I think your explanation is correct.
As a native speaker, it seems more natural to me to leave the "one" or "they" out altogether, since we don't know who they are, and the emphasis is on the program, not the (unknown) people presenting it. "There is a good program being presented at the cinema" is how I would say it. But
What does the English 'program' mean here? It can't mean a television program(me). Does it mean something like a 'choice of options', like the more original meaning of program(me) in English?
If so, would "they are presenting a good selection at the cinema" be a better translation?