"Do you mean that Justin Sun pays his witnesses to manipulate and control the press and information?"

His control is limited to complete domination of the Steem blockchain, as his stake is far and away the largest. All others combined do not equal his ... As far as the press, etc. outside the Steem blockchain, we can both assume he does what he can to influence them to be biased toward whatever he wants them to believe ... Control though? He is not that rich ...

"Does that mean BlockTrades created the Hive blockchain when Justin Sun bought Steemit?"

No, when the "war" with Justin Sun was going into its 2nd month, with no prospect of it ending ... BlockTrades led others to just "dump" the Steem blockchain instead and start over, with their own new blockchain.

Getting your funds back and forth between the Steem and Hive blockchains can be accomplished with Hive account@swap.app. There are other alternatives, but this is the most straightforward and the one I used. Here is a link to that app and posts written about how to use it - @swap.app/posts

Beyond that, buying and selling HIVE tokens or any other crypto begins with exchanging whatever Korean funds you may wish to invest into crypto. Is that what you are asking for help with, as well?