Dickens uses the 'first person past and present spoken' method of narration in "Great Expectations." The story is told (spoken) by the narrator Pip. Sometimes he tells us what happened in the past: "alterations have been made in that part of the Temple since that time." Ch39. Sometimes he tells us what is happening in the present, especially if the incident is very sensational, to make it very vivid and dramatic: The arrival of Magwitch in Ch 39, "As I shut it [the book] ... I was listening."
Another technique which Dickens uses is the technique of 'story within story.' The entire novel deals with the story of Pip, but at the same time diffferent characters tell their stories to Pip. In Ch.7 Joe tells Pip his story, similarly Magwitch tells his story to Pip and Herbert in Ch.42. Both these stories are narrated in a simple and straightforward manner.
However the stories of Miss Havisham and Compeyson and Molly and Estella are narrated in a more complex and roundabout manner in order to create suspense. These stories are pieced together like a jigsaw puzzle and are similar to the stories in detective fiction.