Beowulf: fact or fiction?

The character Beowulf is a seemingly invisible man who defeats evil creatures. In his amazing battle with Grendel, Beowulf fights the demon without any armor or weaponry. In the end of the battle Beowulf wins by literally ripping Grendel's arm off, causing Grendel to retreat to his layer where him and his mom live. Another story would be when Beowulf goes into the layer where Grendel and his mother live to slay Grendel's mother for the murderous doings she had done to the danes. When Beowulf goes into the cave he finds Grendel's mother and fights her. When he kills her, he find Grendel and cuts off the head that he used to kill its mother.

My question is this, is Beowulf fact or fiction? I know of no man that is able to rip off some ones arm out, let alone a demons arm out. In my opinion, i think that Beowulf is a very fun read but a very unrealistic book.