Do we get interest on the interest or do we have to provide the interest in order to get interest on it?
it‘s automatically compounded. no need to withdraw and provide manually!
Interest will automatically compound on both your provided liquidity as well as on the interest rewards you receive.
One thing to note is that while you may earn PRV for staking BTC for example. Your PRV rewards will only earn the same interest rate as the provided liquidity. In this example your PRV rewards would earn at the 11% the BTC is earning at. If you wish your PRV rewards to earn at 28% you would need to withdraw them and deposit as PRV liquidity.