Heart of Darkness End of Part One

Marlow takes off on a french steamer towards the Congo River is switched to another steamer to go up the river. I thought that this was a Belgium Company so why is he on a french boat.  When he is on the second boat he is told about another man that just hung himself on the boat, I think that this is symbol of what life working in the Congo is going to be like, like sucking the life out of him and not wanting to be part of such an awful thing.  Marlow discovers what the Congo is really like and tries to feed on of the native people.  He then meets the account and tells him to pass a note on to Mr. Kutz. Is this note that he is passing on a note about the awful treatments of the native people. When Marlow arrives at the central station to get his boat he found that it has sunken.  Marlow discovers the boat was sunk on purpose. I think that this happen to not allow Marlow to get to Mr. Kurtz.  Marlow gets his boat out of the water and has to wait for equipment to fix it.  A market place burns down and the native people dance.  Why do they dance? Do they dance because this might force out the non-natives?