You can get replacement ear speaker and ring speaker on Ebay very cheap. The contacts on the board might need cleaning with some isopropyl alcohol before you buy any replacement parts.
Check for poor contact with the board or corrosion on the contacts where the main ring speaker contacts touch the board. It could also be a blown component on the board so bear that in mind. There are videos on YouTube and the like of how to take the phone apart as it’s an old phone.