Issues of race and imperialism.
I am assuming that you would like some comments on these issues as they figure in Heart of Darkness, and I can certainly do so. However, in order to get a less general response, it is a good idea to pose a question or provide more specificity than you have right now.
The book is a reflection of the reality that imperialism almost inevitably involves the colonizing of a country of darker-skinned people by a lighter-skinned people. Sometimes there is a racial difference, but not always. The colonizing of India, for example, did not generally involve a racial difference, since Indians have been considered Caucasian by anthropologists and India was occupied by the English and the Portuguese, also Caucasian. But this novella concerns a section of Africa that held black native peoples, and since it is the English colonists and merchants who occupy the area, certainly, there is an issue of race.
Since in the Western world, we tend to use darkness to symbolize evil and lightness to symbolize good, a person might reasonably suppose that the title suggests that Africa is a dark, thus evil, continent, colonized by light, thus good, people, but that is not the case. It is the English who have dark hearts, not the native Africans.
Each "scene" as the narrator travels up the river to the heart of this darkness is carefully selected to show the English in the worst possible light, as a people who treat others inhumanely for their own gains of money and power.
There are those who seem to think that Conrad glorified colonialism and portrayed Africans as savages, but I think a careful reading of the story does not support this.
speamerfam, I partly agree with some of your post but you are mistaken in your use of the word English. Please substitute it for the word 'European(s).' Heart of Darkness was set in the Belgian Congo & although the English were all over the continent of Africa 'as a people who treat others inhumanely for their own gains of money and power', in the case of Heart of Darkness, Conrad was careful to make Belgian colonisation the subject of European inhumanity to Africans for the obvious reasons that English readers could distance themselves from atrocities committed by English colonial administrations. Also, the book is written in English leading me to believe that if Conrad had wrote about brutality within a British colony it would not have been very successful (shrewed marketing). You are not the first teacher to confuse English colonial brutality with European on this forum either!