who wrote it?
It is anonymous.
Gospel of John
 Like the three other gospels, it is anonymous, although it identifies an unnamed "disciple whom Jesus loved" as the source of its traditions. It most likely arose within a "Johannine community", and as it is closely related in style and content to the three Johannine epistles most scholars treat the four books, along with the Book of Revelation, as a single corpus of Johannine literature, albeit not from the same author.
how many chapters does the gospel of john have 21. what is its structure? It has four sections: A prologue, the "Book of Signs", the "book of glory", and a conclusion. The epilogue might not have been a part of the original text. is it reliable historically? According to historians it has some historical value. how is it connected to john the baptist? It is the fourth of the canonical gospels , compiled by John. what is its setting? Initially, it was considered that the gospel was set in a  late 1st century Christian community excommunicated from the Jewish synagogue. However, there has been debates regarding this in recent times. when was it written? Its origin may date back to AD 70 or earlier.
wiki:7674455
Gospel of John [SEP] Introduction
Like the three other gospels, it is anonymous, although it identifies an unnamed "disciple whom Jesus loved" as the source of its traditions. It most likely arose within a "Johannine community", and as it is closely related in style and content to the three Johannine epistles most scholars treat the four books, along with the Book of Revelation, as a single corpus of Johannine literature, albeit not from the same author. The discourses seem to be concerned with issues of the church–synagogue debate at the time of composition.