Thank you for your answer.
I will try to be more specific regarding the context.
The plot of the story is about the life of Lars Hertervig. A Norwegian painter of the 19th century. He suffered from schizophrenia, but apart from this mental disorder, he suffered a cruel prank played by his fellow students. It is shown that the classmates laughed at him in the book for being a Quaker and poor. This fatal experience in Germany led him to end up in an Asylum in Norway. Dying at the age of 72.
Fosse was inspired by the tumultuous life of this painter, and decided to write Melancholia, trying to put the reader in the painter's shoes. Following Fosse's writing technique, Lars Hertervig communicates himself in two different ways: with the characters around (dialogue) and speaking alone (soliloquy). When he speaks alone in the street or at home, he suffers from melancholia. He seems not to be really happy in Germany and misses the old days in Norway.
The reason why the father of Hertervig walked towards the pier is unknown. What I can tell you is that the pier itself always comes in the 'hallucinations' of him. Sometimes his father appears, another his sister, for example. In my own opinion, I think it is not a dreamlike scene. He experienced it in real life when he was young and lived in Norway.
For example: there is a scene in the book where his classmates are laughing at him because one of them says his family is Quakers. Instead of getting angry with them, he experiences a sense of melancholia (the pier appears again. His sister and mother are there, in silence. Smiling) and then suffers a mental breakdown in front of his classmates: he starts to shout 'mother' and 'sister' without control.
(The mother and sister remain in silence at the pier in this breakdown of the painter).
And the bullies start to saying to him: why are you talking alone? Who is Elizabeth? (Elizabeth is the sister of Hertervig). Here I feel that the noise of the bullying crash with the silently melancholia of Hertervig.
So if the narrator is on the pier daydreaming, using his imagination, then it's better that you the reader, use your imagination to better understand the situation described. — Metaphysician Undercover
I agree. But what makes me wonder about how Fosse wrote the book is whether the silence is a reference to death (his parents and sister passed away and he feels alone) or the inability to say to them that he wants to go back to Norway. In this novel, the silence is a key factor and, most of the time, is confusing because even the protagonist feels scared of why his family remain in silence at the pier.