What does the character Marlow in "Heart of Darkness" primarily struggle with?

Marlow's primary struggle in "Heart of Darkness" centers on his identity as a civilized individual. Throughout his journey into the Congolese interior, he confronts the stark contrasts between European imperialism's so-called civilization and the primal instincts and brutality he witnesses in the jungle. This internal conflict forces him to examine not only the moral implications of colonialism but also his own ethical beliefs and societal values as he grapples with feelings of alienation, disillusionment, and a deeper understanding of humanity's darker nature.

While aspects of wealth, adventure, and romantic relationships may briefly appear in the narrative, they do not encompass the crux of Marlow's existential crisis or the philosophical inquiries that dominated his expedition into the heart of darkness. His reflections and realizations about civilization, savagery, and his own place within these constructs define his character and the overall themes of the novella.