How to make a successful login session?

At first I tried to bring the data that was entered during the registration to a new activity, but change your mind, I just want that in case of having a successful session start, when I hit the "enter" button, send me to another activity I'm connected to a database (mysql) 1) I know that to bring the data from the database to compare them with the data entered in the login activity, that goes in the if but I do not know how to develop the code (I'm new programming)

Note: In my database the user is called "user_name" and the password is "password" The activity in which I find myself is called "login" and to which I would go in case of a true real comparison "Welcome" This is my Login code (where you enter the data to log in):

public class Login extends AppCompatActivity {

TextView tv_registrar;
EditText etapellidos,etusuario, etClave;
Button entrar;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_login);
    /*etnombre = findViewById(R.id.nom);*/
    etapellidos = findViewById(R.id.ape);
    etusuario =  findViewById(R.id.usu);
    /*etcertificacion = findViewById(R.id.cert);*/
    etClave =  findViewById(R.id.pass);
    entrar=  findViewById(R.id.entrar);



    tv_registrar=findViewById(R.id.tv_registrar);
    tv_registrar.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View view) { /*enlace de texto registro con activity Registro*/
            Intent intentReg = new Intent(Login.this, Registro.class);
            Login.this.startActivity(intentReg);
        }
    });

    entrar.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View view){

            final String user_name=etusuario.getText().toString();
            final String password=etClave.getText().toString();

            Response.Listener<String> responListener = new Response.Listener<String>() {
                    /*Response.Listener<String> responseListener = new Response.Listener<String>() {*/
                @Override
                public void onResponse(String response) {
                    try {
                        JSONObject jsonResponse = new JSONObject(response);

                        boolean success = jsonResponse.getBoolean("success");
                        if (success){  
                            Intent intent = new Intent(Login.this,Bienvenido.class);
                            Login.this.startActivity(intent);
                        }else {

                            AlertDialog.Builder builder = new AlertDialog.Builder(Login.this);
                            builder.setMessage("ERROR EN EL INICIO DE SESION")
                                    .setNegativeButton("Retry",null)
                                    .create().show();
                        }
                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                }
            };

            SolicitudDeInicio solicitudDeInicio = new SolicitudDeInicio(user_name,password,responListener);

            /*CLASE PARA COMUNICARSE CON VOLLEY*/
            RequestQueue queue = Volley.newRequestQueue(Login.this);
            queue.add(solicitudDeInicio);
        }
    });


}

this is my conecion.php file:

<?php
$con = mysqli_connect("localhost", "root", "", "usuarios");

$user_name = $_POST["user_name"];
$password = $_POST["password"];

$statement = mysqli_prepare($con, "SELECT * FROM usuarios WHERE user_name = ? AND password = ?");
mysqli_stmt_bind_param($statement, "ss", $user_name, $password);
mysqli_stmt_execute($statement);

mysqli_stmt_store_result($statement);
mysqli_stmt_bind_result($statement,$name,$surname, $user_name, $course,$password);

$response = array();
$response["success"] = false;  

while(mysqli_stmt_fetch($statement)){
    $response["success"] = true;  
    $response["name"] = $name;
$response["surname"] = $surname;
    $response["user_name"] = $user_name;
    $response["course"] = $course;
    $response["password"] = $password;
}

echo json_encode($response);

? >

thanks