Dynamic translation of QT c++

I want to make all the labels in my app translated from Russian to English by selecting the option in QComboBox or by pressing a button. Found the instructions: https://evileg.com/ru/post/153/ It seems to have done almost everything as there MainWindow.cpp:

 void MainWindow::on_comboBox_currentIndexChanged(int index)
    {
        if (index == 0){qtLanguageTranslator.load(QString("QtLanguage_") + QString("ru_RU"));}
        else{qtLanguageTranslator.load(QString("QtLanguage_") + QString("en_EU"));}
        qApp->installTranslator(&qtLanguageTranslator);        // Устанавливаем перевод в приложение
    }

void MainWindow::changeEvent(QEvent *event)
{
    // В случае получения события изменения языка приложения
    if (event->type() == QEvent::LanguageChange) {
    ui->retranslateUi(this);    // переведём окно заново
    }
}

Mainwindow.h:

protected:
    // Метод получения событий в главном окне приложения
    // В нём будет производиться проверка события смены перевода приложения
    void changeEvent(QEvent * event);
private:
    Ui::MainWindow *ui;
    QTranslator qtLanguageTranslator;

.pro:

TRANSLATIONS += QtLanguage_ru.ts
TRANSLATIONS += QtLanguage_en.ts

I set up transfers for them, made lrelease. But then it does not work to change the language by selecting the option or even set the English language (by default default Russian). What did I do wrong? Or is there an easier option?