1. Why is Marlowe telling us this story?

Marlow's purpose in telling this story is to chronicle of imperial rule at the time. From the start, the audience understands that this is to be a recollection. For the modern reader, it's important to know a bit about European colonialism (hopefully you've studied this in class). Thus, Marlow's metaphor is that the heart of darkness does not necessarily lie in the depths of the "savages" in the Congo, but rather in the hearts of the white men who exploit it. The bitterness of Marlow's recollection suggests Conrad's strong bias against colonialism, which he seems to be imparting to the reader by expressing Marlow’s difficulties.