Visa C-3-4 extension

Hello, I am a citizen of Tajikistan and I recently received a C-3-4 visa for South Korea that is valid for one month. Previously, the embassy issued C-3-4 visa for up to three months, or two months with the possibility of extension through a border run. Currently, only one-month C 3-3-4 visas are being issued. I heard that it might be possible to extend the visa for one more month after the initial one-month period expires. Has anyone done this recently or know how to do, what is the procedure? (편집됨)