This is the 10615th most frequent Polish word.
dokumentalnego
"Dokumentalnego" means "documentary" (adjective).
The word 'dokumentalnego' in this sentence modifies the noun 'film'. It is used in its adjective form to describe the genre or type of the film, aligning with grammatical agreements.
Właśnie obejrzałem film dokumentalny o historii starożytnego Egiptu.
I just watched a documentary film about the history of ancient Egypt.
In this usage, 'dokumentalnego' is in its adjective form and modifies the noun 'filmu', indicating that the film being referred to is of the documentary genre.
Produkcja dokumentalnego filmu wymaga wielu badań i przygotowań.
The production of a documentary film requires a lot of research and preparations.
Here, 'dokumentalnego' modifies the noun 'programu' in its adjective form, describing the type of the program.