Why ViewController back buttons don't work on Xcode?

Hi I’m learning Xcode to make ios application. I have problem

This is error code ->
Thread 1: "-[UIViewController back2:]: unrecognized selector sent to instance 0x14fb0e270"

first ViewContorller code ->

import UIKit

class ViewController: UIViewController {


    @IBAction func moveByNavi(_ sender: Any) {
        guard let uvc = self.storyboard?.instantiateViewController(withIdentifier: "SecondVC") else {
            return
        }
        
        self.navigationController?.pushViewController(uvc, animated: true)
    }
    
    @IBAction func movePresent(_ sender: Any) {
        guard let uvc = self.storyboard?.instantiateViewController(withIdentifier: "SecondVC") else {
            return
        }
        
        uvc.modalPresentationStyle = .fullScreen
        self.present(uvc, animated: true)
    }
}

Second ViewContorller code ->

import UIKit

class SecondViewController: UIViewController {
    
    @IBAction func back(_ sender: Any) {
        self.presentingViewController?.dismiss(animated: true)
    }
    
    @IBAction func back2(_ sender: Any) {
        _ = self.navigationController?.popViewController(animated: true)
    }
}

Whenever I click back and back2 buttons on second view controller, My simulator stop. And show that error code on appDelegate.

I Checked connections inspector of second view Controller. back buttons connection is connected well. I don’t have rests of connection as well.
How can I fix my code?