Everyone knows the world has a total of 21 million bitcoins and a total of 17 million bitcoins have been mined. So what happens when 21 million bitcoins are exploited?

As far as I know miners have two sources of income when exploiting bitcoin that is:
1. Be rewarded with bitcoin from the number of deals they handle.
2. The main reward: the bitcoin reward, for each bitcoin block to be exploited.

When 21 million Bitcoins are mined, the second source of income will be gone. So how will the bitcoin network do when there are no miners? I do not think that with only a single source of income, it may be profitable for them when the Bitcoin price goes down.

I look forward to receiving an explanation from someone and thanks!