From the text:
At the station, Kurtz is described to Marlow in the following way:
'In the interior you will no doubt meet Mr. Kurtz.' On my asking who Mr. Kurtz was, he said he was a first-class agent; and seeing my disappointment at this information, he added slowly, laying down his pen, 'He is a very remarkable person."
In the next quote, we can infer that Marlow is "sick" of hearing about Kurtz.
?"There were rumors that a very important station was in jeopardy, and its chief, Mr. Kurtz, was ill. Hoped it was not true. Mr. Kurtz was . . . I felt weary and irritable. Hang Kurtz, I thought. I interrupted him by saying I had heard of Mr. Kurtz on the coast. 'Ah! So they talk of him down there,' he murmured to himself. Then he began again, assuring me Mr. Kurtz was the best agent he had, an exceptional man, of the greatest importance to the Company; therefore I could understand his anxiety."