What will happenwhen all the Bitcoin is mined

I apologize in advance if there is a simple explanation for this. Being a noob in this space I often find the tech talk a little tough to get my head around but if anyone can enlighten me that would be awesome.
So bitcoin has a finite amount and for it to work through Proof of Work it needs to be mined . You can earn Bitcoin through mining. One of the major problems with Bitcoin is that the fees are not scaling with the rise of the amount of work being done to prove the transaction on the blockchain the fees are increasing. Not withstanding the widespread adoption and completion of improvements such as Lightning, Atomic Swaps and Segwit 2x. What will happen when all the Bitcoin is owned. The only way to get it will be if someone is to sell it to you and that supply demand market is going to make you pay. Regardless of how cheap it actually cost, surely miners will add high transaction fees.
Thoughts anyone?