Can someone please help me find out the background problems in The English Patient?

You are right in asserting that Ondaatje's work is
complicated.  It is.  No doubt about it.  You will have become very used the idea of
narratives flowing into one another with different backgrounds that converge into
reality.  This is tough. 

The fundamental context of all of
the characters in the book is World War II.  Different elements of this conflict present
themselves to different characters.  Yet, in the end, all of the primary characters find
themselves struggling with the conditions of war and the impact it leaves on the human
being.  Hana is a Canadian nurse during the war, and one who struggles with death from
both a universal and personal perspective.  She is haunted by the constant presence of
soldiers' deaths, and her inability to stop it. At the same time, she is haunted by her
own father's death and the death of her unborn child via abortion.  Kip is an explosives
expert, working for the British army, yet frustrated at the British control of India and
the Western colonization that has suppressed his country.  Caravaggio is an Canadian spy
of Italian descent, and a victim of German torture.  The English patient might be the
most complex of all of the characters here, though.  He is considered English because of
his grasp of language.  Yet, his identity is not really established in terms of his
affinity with political sides.  He is a brilliant cartographer of the North African
desert, who is in love with Katherine Clifton, the British wife of one of the Patient's
colleagues.  After the tragedy in the desert, he is unable to save Katherine because of
his name.  He can only go back after two years, to retrieve her body, and in doing so,
he suffers the accident that disfigures him.  All of these character narratives are
woven with the background of the war, and expressing its pain and brutality becomes the
primary focus of the novel.