Hello. Although you haven't referenced a text, you haven't submitted any questions about them. This makes it impossible for me to provide any answers. However, I will try to help you as best I can by explaining what these references mean.
All references shown can be found in "Life on the Mississippi" written by Mark Twain. In this book, Twain presents his experiences when he was being trained to become a steamboat captain when he was 21 years old. In all the references presented above, we can see how Twain mocked himself and joked about his own intellectual capacity.
When he tries to drive the boat for the first time, he is very impressed, but finds his ability ridiculous.
When he doesn't show up for the first night watch, he starts to mock his ability to be responsible and makes a lot of self-deprecating jokes.
When he finds out that he will need to learn the entire river, he also makes self-deprecating jokes and scoffs at the whole situation.
