What congrade hopes to achieve in chapter one ?

THere are a few things at play here. The beginning deals with the whole theme of "darkness". It is initially mentioned in the context of maps, where places of darkness have been colored in once they have been explored and settled by colonists. There in lies one of the major themes of the story. Did these unexplored places become dark only after colonial arrival? The audience recognizes that this is to be a recollection tale. Marlow's sallow skin and sunken cheeks do not portray him as healthy or happy. He has had the chance to explore, but apparently the experience has ruined him. This is Conrad's way of arranging the overall structure of the novella. Once this for boding tone is set Conrad takes us into "the heart of darkness". Here in the very alien Congo river basin, we begin to study the many shades of darkness that Conrad explores. We see "Black shapes" crouch on the ground, and "creatures" walk on all fours to get a drink from the river. They are called shadows: reflections of humans, not substantial enough to be real. This, however, is the superficial shade of darkness. The whole understanding of imperial thought over colonization and exploitation is introduced in Part one but only comes into focus later in the novella.