I didn't read that book. Sorry.
Internal conflict is conflict that, like the name suggests, comes from inside the character. The problem comes from some sort of internal debate, indecision, self-doubt, etc. Man vs. Self conflict. The character might have a mental or emotional problem that they must overcome to achieve their goal.
External conflict is a conflict that comes from outside a character's control. Man vs. Man, Man vs. Machine, Man vs. Society, Man vs. Nature, Man vs. Supernatural (Gods, fate, monsters, etc). It is a conflict that is outside a person's control, but one they must overcome nonetheless. Think villains in fairy-tales, or dystopian novels where a person or group has to rise against an oppressive government for some examples.
Most stories will combine both types of conflict, often with one causing or feeding into the other. Pretty much every story whether it's a novel, movie, video game, etc, will have some sort of conflict, and most will have both. I'll leave specific examples to you.
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The bank teller is flat because he doesn't change
I think the answer is the narrator’s thoughts
