They are starving and mistreated, and therefore cannot work efficiently, this is due to the treatment from the Europeans, which only hurts their system also, that don't gain from the mistrewatment of slaves either.
Another example is the slowly decreasing of hierarchy in Africa. Kurtz is to be in charge of finding ivory, but instead, he abandons his job and in the mean time loses his civil traits.
Another example of the futility of the Europeans is that they're not good they're not good at navigating and end up taking longer. Marlow has difficulty trying to complete his task because of the stupidity in navigating.
Framework story structure:
Heart of Darkness,frame story structure is a story within a story. Typically authors will use this method to represent a story of their own experience. The author may be wanting to give a deeper meaning to the story representing his own life in a different situation but the same idea. Instead of two hundred mile tramp he may be wanting to express the long ride its taken him to get where he is now and it feels as if he has traveled through many jungles, forests, across river, and