Yeah I definitely agree with that! The 2nd passage confused me a bit, but I managed to pull some parts out of it - mainly Marlow's description of the trees and the 'ringing ivory' part 
What ideas did you write about? 
Started off slow with a page and a bit on how conrad belives the flaws of the human condition are not unique to the white men (i.e. everyone is flawed); used the 'white worsted' on the native to compare to the Accountant's silk tie to show they had the same goals (to create sense out of the mystery of the wild or whatever) and hence had the same objectives, although arguably the Europeans executed it a lot better, no pun intended. It was part analysis, part set up for the rest so I wouldn't have to clarify every time I mentioned the human condition because it was a big part of my work.
Second paragraph was a whole bunch of similar things smashed together - europeans dehumanising the natives so that they could treat them as their new found technology without guilt; even though it wasn't part of the passages I drew on Marlow's lie to Kurtz' betrothed to show that the whites were capable of sympathy and the company's behaviour was calculated in favour of increasing the materialistic wealth of an individual rather than the society, their 'flabby devils', so to speak.
Third was Marlow, and by extension, Conrad, being aware of this detestable behaviour but participating anyway; justifying stuff like getting the cannibals to push the steamboat with his inexorable draw to Kurtz, like he'd never joined the Company for anything else. Basically about Conrad acknowledging the flaws of the human condition that he couldn't escape and accepting that ultimately while we have an influence on our lives we cannot escape death (as even kurtz couldn't, 'kicking himself free of the earth', 'kicking the earth to pieces', etc.) so our efforts to adhere to any moral standard are meaningless.
Was going to do four paragraphs but I was 5 pages into the response booklet at that point and I thought it'd reached its natural end, hopefully

. It was a very melancholy essay, but I think Conrad's writing definitely lends itself to introspection and cynical undertones.
What did you write about? A lot of my mates went for the journey into the self deal. Certainly worked well with kurtz' death being one of the passages.