How long did it take Beowulf to sink to the bottom of the lake?

Why is Grendel's mother unable to harm Beowulf when she first attacks him?

What did Beowulf find that helped him win the battle?

After Beowulf returns home, he becomes king and rules for 50 years, but he leaves to face a monster. What monster does he leave to face?

When Beowulf is almost defeated, who is the young warrior who stays with him to fight?