Difficulties

On the river when Marlow and his men and the 'cannibals' are moving, they encounter the fog and hear the voices and then they get attacked. I know that was a brief summary but my point or lack thereof is 'what just happened?' After I finished that passage I was confused as to why Conrad had put the arrow attack scene in that order. They ask, "Are they going to attack us?" Then they don't and then they do. 

I am just confused on the significance/meaning of this entire passage. I know its important (it might be that gut feeling you get after being in English classes for so long) I just don't understand. What is the purpose, why are the 'cannibals' and the natives so opposed to each other (are they from different tribes)? 

Juicy Quotoure

From page 69

"They were men enough to face the darkness."

This quotation hearkens back to what we had just studied and discussed in King Leopold's Ghost, mainly the psychology of why these men conquers Africa. Men's worth relied heavily on their masculinity and their overall 'manliness'. In the context of Heart of Darkness I believe that this will feature heavily.

This hints to a future where Marlow may or may not have to 'man up' in order to survive and make history. Conrad makes a reference to the 'darkness' of Africa here and mentions how the white men had to wrestle and tangle and conquer the darkness, being man enough to do so.