Uncle Jaber's boat

The novel tells about the adventures of the famous YouTuber, Yehia Azzam, and the most famous writer, Mohamed Ismat (the horror fan), and how their friendship began, and how Yehia Azzam, or Yaya, transformed from a content creator to a writer with primarily fictional adventures, in addition to some real events that actually happened. Who is uncle Jaber? What is the matter with them? Are the events really real or fictional?