I was reading the book of Nahum and it was speaking about Nineveh. Is the book of Nahum foretelling the destruction of Nineveh, for which the people of Nineveh averted by repenting of their sins, or is Nahum talking about an event that happened after Jonah's time?
Nahum takes place about 140 years after Jonah. Jonah preached, they repented, they later returned to wickedness, and Nahum prophesied judgement. Ironically, Nahum means "comfort."
Jonah shows a 7-8th century BC background (though some argue the current form came much later, around the 4th century BC). And 2 Kings 14:25 mentions a prophet named Jonah son of Amittai during the reign of Jeroboam II (786-746 BC).
He restored the border of Israel from Lebo Hamath in the north to the sea of the Arabah in the south, in accordance with the word of the Lord God of Israel announced through his servant Jonah son of Amittai, the prophet from Gath Hepher. [NET Bible]
Nahum seems to date from ca. 615 BC. This date is defended on the grounds that the destruction of Nineveh came about in 612, and Nahum 3:8-10 compares Nineveh's coming destruction to Thebes already-happened destruction of 663 BC.