[Unity] Load Scene async

AsyncOperation async;
IEnumerator LoadNewScene(string stringZaladuj)
{
    yield return new WaitForSeconds (3);
    async = Application.LoadLevelAsync(stringZaladuj);
    async.allowSceneActivation = false;

    while (async.progress < 0.9f)
    {
        yield return null;
    }
    Debug.Log ("the Game has been loaded");

    while(!Input.GetMouseButtonDown(0))
    {
        yield return null;
    }

    async.allowSceneActivation = true;
}


 IEnumerator LoadNewScene(string sceneName)
    {
        AsyncOperation async;
        async = SceneManager.LoadSceneAsync(sceneName);

        while(!async.isDone)
        {
            Debug.Log(async.progress);
            float progress = Mathf.Clamp01(async.progress / .9f);

            loadingText.text =  string.Format("Loading {0}%",async.progress * 100); //"Loading "+ (progress * 100) + "%";//
            yield return null;
        }
    }