How can I implement a button to change language on Android Studio?

I'm developing a multi-linguistic app, because it's oriented to a very diverse public. I tried to make it through a method I found googling, but while it seems to have some sense (sorry in advance, I'm not a native speaker nor a real programmer), I didn't get it to work. The method is

package com.example.donafelicidad;

import android.content.res.Resources;
import android.content.res.Configuration;

import java.util.Locale;


public class LanguageHelper {

    public static void changeLocale(Resources res, String locale) {

        Configuration config;
        config = new Configuration(res.getConfiguration());

        switch (locale){
            case "es":
                config.locale = new Locale("es");
                break;
            case "qu":
                config.locale = new Locale("qu");
                break;
           }
        res.updateConfiguration(config, res.getDisplayMetrics());
    }
}

I'm applying this method with the buttons, referenced as CHNG_QU, and CHNG_ES:

CHNG_QU.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                LanguageHelper.changeLocale(getApplicationContext().getResources(), "qu");
                Intent intent = new Intent(MainActivity.this, MainActivity.class);
                startActivity(intent);
            }
        });

        CHNG_ES.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                LanguageHelper.changeLocale(getApplicationContext().getResources(), "es");
                Intent intent = new Intent(MainActivity.this, MainActivity.class);
                startActivity(intent);
            }
        });

I changed manually the locale settings, and tried it. It changed perfectly to the other language, so I guess that the Strings are well done. Any feedback about how to handle this would be greatly appreciated, even if it's necessary to re-do the entire code. Please use simple terms for a unexperienced guy who is just doing his best.

As a side note, I didn't use other threads of questions because most of what I found was deprecated.

Lingver is a library made to force your app to use the locale resource files you want.

In the documentation, I found this blogpost that implements it while explaining every step, I hope you find it useful.