When I saw the prices of crypto currencies there is almost every coin's price fell upto 20%.Do you think this is just happening due to South Korea's ban over crypto currencies or there is other reasons for that.
I hope the condition will be back normal soon but I am worried a lot.

Do not worry, the dump in the crypto currency market is inevitable. There will be a pamp, you just need to wait. Do not panic or sell your coins at low prices.