Guru Nanik was a confused man who kept wandering in search of wealth.
The book ascribed to him GARANTH SAHIB was written by his Sufi friends who were aspiring to claim prophethood in the 16th century. The book is not understandable even to scholars of Sikhism. It was authored half a century after Nanik's death.
See Dr. Shabbir Ahmed's book HINDU AND RAM RAJIYA, Urdu and English.