China was main mining center in the past but it has put a complete ban on bitcoin mining which has lead to hashrate distribution across the globe and now China is no longer biggest player.You can check this article for more details : https://worldpopulationreview.com/country-rankings/bitcoin-mining-by-country


Moreover Mining is a process through which new coins come into circulation not confirming the transactions and whenever a block is found the transactions are added in that block in blockchain of which the transaction fees goes to miner along with the block rewards.