And I hardly find any one who has to comment on the "contents" of Gospel of Barnabas,
The Gospel of Barnabas contains many gross errors of history and geography:-
It says that Jesus was born when Pilate was governor of Judea
It tells us that Nazareth is a seaport and has Jesus sail there from Jerusalem
It has Jesus preaching from the pinnacle of the Temple
It describes Jesus as going UP to Capernaum from Nazareth
It describes Elisha talking to the Pharisees, despite the centuries between them
Similarly it has Hosea talking to Haggai
It describes Herod as an infidel, whereas he was actually Jewish by religion
It describes Summer as a time of fruit and harvest - In Israel it is too hot for these.
The Gospel of Barnabas also contains many anachronisms:
It contains short quotations from Dante
It describes the Jubilee as taking place every hundred yrs - correct in Catholic Italy and Spain but not in classical Judea
The social environment is a mediaeval feudal system, not first century Palestine.
It has wine stored in casks, not amphorae or wineskins
Men wear "hosen", mediaeval leggings, rather than tunics and cloaks.
Origins of the Gospel of Barnabas
The manuscript of the Gospel of Barnabas was originally produced by one Mustafa of Aranda who had been forced to convert to Catholicism by the inquisition. He claimed to have translated it from a manuscript given to him by one Fra Marino, a person who was never produced. In view of the failings of the document, it is almost 99.9% certain that it was Mustafa of Aranda who invented the whole document as a way of getting at the Catholics who had forced him to convert. Certainly the language and history in it identifies southern Europe, and probably Spain, as the place of origin of the work.
Incidentally, did you know that the Quran really does endorse the canonical Gospels?
Let the people of the Gospel (Injil) judge by what God has revealed therein. If any do fail to judge by what God hath revealed they are those who rebel.(Q 5:50)
If thou wert in any doubt as to what we have revealed unto thee, then ask those who have been reading the Book before thee (Q10:94)
see also Q5:46,47; 7:169,170; 40:69,70.
These passages are very clear in what they say. The Gospels were available at the time of Muhammad, and they were considered to be inspired by God. We know from manuscript evidence that the New Testament of the 7th century was the same as the current New Testament (and the Old Testament is similarly unchanged).