You are only allowed to ask one question so I have had to edit your question down as you asked several. I am not entirely sure I understand your question. Which society are you referring to precisely? If you are talking about the Africa that we are presented with, I think the chances of resolution in the novel are slim if not non-existent. It is clear throughout this text that Africans are presented as dehumanised animals, nothing more than objects that whites feel they have the power to use, exploit and throw away at their will.
An example of this is the "grove of death" that Marlow sees, where Africans are dying and are described in ways that show their importance:
"Near the same tree two more bundles of acute angles sat with their legs drawn up. One, with his chin propped on his knees, stared at nothing, in an intolerable and appalling manner: his brother phantom rested its forehead, as if overcome with a great weariness; and all about others were scattered in every pose of contorted collapse, as in some picture of a massacre or a pestilence."
This description is made all the more horrifying by the accountant with his neat and impeccably clean white-starched suits that he wears. Resolution, then, seems to be an unattainable goal in this novel.