Pass sentences by voice to text c #

I'm finishing a voice recognition application in c# , but it recognizes only words (not sentences), besides that some of the words that the program recognizes are not the ones I pronounce verbally, I would like them to help me so that the program can recognize phrases and sentences, and also recognize the words correctly.

Here is the code that I carry.

public partial class MainWindow : Window
    {
        SpeechRecognitionEngine _Recognition = new SpeechRecognitionEngine();
        public MainWindow()
        {
}
}

private void btEscuchar_Click(object sender, RoutedEventArgs e)
        {
            _Recognition.SetInputToDefaultAudioDevice();
            _Recognition.LoadGrammar(new DictationGrammar());
            _Recognition.SpeechRecognized += _Recognition_SpeechRecognized;
            _Recognition.RecognizeAsync(RecognizeMode.Multiple);
        }

Greetings.