Grendel came to Herot to kill because of the loud singing and dancing going on and kills 30 men.
The Battle With Grendel's Mother
They fight furiously until Beowulf rips Grendel's arm off with his bare hands and Grendels gets away but ultimately get away
Beowulf's Last Battle:
Bent on revenge for her fallen son, Grendel's mother came to Herot and took Hrothgar's best friend and Grendel's Claw.
Beowulf takes the challenge of killing Grendel's mother and the men follow him. They fought underwater and Beowulf eventually kills her and reaches back to the top.
Beowulf's last battle is against a dragon that is protecting treasure. Beowulf is also very old and the only person to help him is Wiglaf, which later becomes King because Beowulf dies from this battle.
The Geats build the tower in honor of Beowulf which is what he wanted so people could see it from far away and he is cremated. Wiglaf is now King of the Geats.