what happens between grendel and beowulf in parts 6-11?

The meeting between Grendel and Beowulf happens in chapter 11. Basically everybody is asleep when Grendel comes lurking into the great hall, "Then from the moorland, by misty crags, with God’s wrath laden, Grendel came." Beowulf is hiding and watching. Grendel picks up a sleeping warrior and has a snack, straightway he seized a sleeping warrior "for the first, and tore him fiercely asunder, the bone-frame bit, drank blood in streams". Beowulf and Grendel have an epic battle. Beowulf’s demon armour is pretty strong (it is really a spell that is resistant to swords) but Beowulf manages to rip off Grendel's arm from its socket. Grendel retreats to his swamp cave to die.