Ye s it is Korean people are buy a medicine at pharmacies I'm use.
But big hospital doctor's prescription have buy a medicine.
Here's your first corrected composition, Jimmy. Please take a look at the corrections below. 
Can people easily buy medicine at Korean pharmacies even without a doctor's prescription? Explain.
Ye s it is Korean people are buy a medicine at pharmacies I'm use.
But big hospital doctor's prescription have buy a medicine.
>>> Yes, in Korea, people can buy medicine at pharmacies. But for medicines from big hospitals, a doctor's prescription is required.
>>> OR: In Korea, people can purchase medicine at pharmacies. However, medications prescribed by doctors at major hospitals require a prescription.