Once Grendel came into the Mead Hall and killed multiple people several nights in a row. Hrothgar called in Beowulf to take care of Beowulf.
The night Beowulf was waiting for Grendel to come into fight him. Grendel then hallucinates and gets defeated by Beowulf. Beowulf pulled off his arm and he bleed out until he died.
Once Grenedel's mom heard that Grendel died. She came to the Mead Hall and killed the kinds adviser, Aeschere. Hrothgar then send Beowulf to hunt her down and defeat her next. He traveled to the Lake of the Monsters where we defeated Grendel's mom.
Once Beowulf defeated Grendel's mom is rewards was that he was worshiped and honored, and took back Grendel's head to king, Hrothgar.
At the end he was back home and he got bit by a dragon in his neck starting to bleed out and later died looking his treasure.