How to close a WebView automatically after a certain event (Android)?

I am working with TypeForm forms that I show them through WebView in my application.

What I'm trying to do is close the WebView after they finish the form.

When the form is completed on the screen, a text appears thanking. How can I take that text and in the case that appears close the WebView.

This is the code I have made.

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_type_form_rest_of_day);

    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);

    setSupportActionBar(toolbar);
    ActionBar actionBar = getSupportActionBar();
    actionBar.setDisplayHomeAsUpEnabled(true);
    actionBar.setTitle("");

    Bundle datos = this.getIntent().getExtras();
    assert datos != null;
    user = datos.getString("email");

    WebView myWebView = (WebView) findViewById(R.id.webview);
    WebSettings webSettings = myWebView.getSettings();
    webSettings.setJavaScriptEnabled(true);
    myWebView.setWebViewClient(new WebViewClient());

    if (Locale.getDefault().getLanguage().equals("en")) {

        myWebView.loadUrl("http://cliente.typeform.com/to/U0mcRV?user=" + user);
    }else{

        myWebView.loadUrl("http://cliente.typeform.com/to/U7o3PU?user=" + user);
    }
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    if (item.getItemId() == android.R.id.home) {
        finish();
        return true;
    } else
        return super.onOptionsItemSelected(item);

}

Greetings!