Please be advised that Villa level and Boss level are different feature of the game and they are also have different ways to level up.
Villa Level - to level up, you need to meet the requirements like building upgrades or invest to level them up.
Boss Level - need to use Boss experience to level up. Please keep in mind that the higher level of your Boss level the higher it will cost to level them up.
Friendly Tip: In case you find this article of no help, please do not choose to resolve and contact our customer support instead, we are here to help!