What did Joash focus on repairing?

Answer: The temple

Joash told the priests to collect the sacred money brought into the house of the LORD and use it to repair the temple.

“Then Joash said to the priests, “Collect all the money brought as sacred gifts into the house of the LORD—the census money, the money from vows, and the money brought voluntarily into the house of the LORD. Let every priest receive it from his constituency, and let it be used to repair any damage found in the temple.””— 2 Kings 12:4-5 (BSB)