What useful information does the Russian Sailor provide about Kurtz and the situation at the Inner Station?

 The Russian says the ship was attacked because the natives do not want Kurtz to leave with the crew, for he has broadened everyone's mind there. The Russian says that he has gone so far that he does not know if he will ever get back. Apparently he has been alone with Kurtz for many months. His sense of adventure is pure, and glamour urges him onward. The Russian remembers the first night he spoke to Kurtz: he forgot to sleep, he was so captivated. Kurtz made him "see things." He has nursed this great man through illnesses and has accompanied him on explorations to villages. Kurtz has raided the country by securing the cooperation of the nearby tribe, whose members all adore him. He loses himself in ivory hunts for weeks at a time. The Russian disagrees that Kurtz is mad. Even when this bright-eyed adventurer was dismissed by his mentor, he refused to go. Kurtz went down the river alone to make another ivory raid. His illness acted up, so the Russian joined him in order to take care of him.