For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Siddhartha is unfulfilled and seeks greater spiritual fulfillment.
Siddhartha lives a life of deprivation with the Samanas, and then lives a life of material and sexual pleasure.
After a near suicide, Siddhartha begins life as a ferryman. After listening to the river, he attains enlightenment.