Quick answers

What is Congo diary and other uncollected pieces about?

The Congo Diary by Joseph Conrad describes his trip up the Congo River as a steamer captain in the employ of a Belgian trading company, an episode that would inspire his novella, Heart of Darkness. [this sentence was partly inspired by the Wikipedia entry for Joseph Conrad.]

When was Congo diary and other uncollected pieces published?

Congo diary and other uncollected pieces was published in 1978.

Who made Congo diary and other uncollected pieces?

Congo diary and other uncollected pieces was written by Joseph Conrad.