Kierkegaard's writing in this section may seem confusing and unclear. He never offers a straightforward definition of his key term, "despair." Instead, he provides a series of different comments and examples and leaves it up to the reader to make sense of what he is saying.
If you were to write something like this your professor would probably fail your paper. Experts on Kierkegaard, however, see this style as an integral part of Kierkegaard's philosophical message and have gone to great lengths to explain what it contributes to his philosophy.
The most common explanation of what Kierkegaard is up to is that, unlike the scientists and scholars he criticizes, Kierkegaard is not trying to communicate straightforward facts, but rather to provoke a new state of awareness in his readers. He therefore writes in an circuitous manner that is meant more to provoke reflection than to communicate clear ideas.
Some Kierkegaard experts have argued that the format of The Sickness Unto Death--its complex structure of parts and sections and subsections, its many definitions and categories--is meant to be an elaborate parody of Hegel and other philosophers who think that philosophy can use precise terms and concepts to develop a complete picture of the world. According to this interpretation, Kierkegaard's writing is meant to show us that rational analysis and interpretation can't always provide clear answers. Just as we can't develop a precise interpretation of what Kierkegaard is saying, so perhaps can we not develop a precise understanding of spiritual issues.
As you read, you should keep these interpretations in mind. Always pay attention to Kierkegaard's style and think about what it communicates to you. Does Kierkegaard seem to want to provoke reflection? Or does he have something specific to say? Is he poking fun at people who make intricate arguments? Or is he actually making an intricate argument?
To the extent that Kierkegaard does have something specific to say, Part I.A. appears to offer an account of what it means to be a human being, followed by an account of what he means by "despair."