Update Navigation Url

using (var contextNavigation = new ClientContext(<siteURL>))
{
    contextNavigation.Credentials = new SharePointOnlineCredentials(UserName, SecurePass);
    Web web = contextNavigation.Web;
    contextNavigation.Load(web, w => w.Navigation);
    contextNavigation.Load(web);
    contextNavigation.ExecuteQuery();

    //Start working on Navigation
    NavigationNodeCollection lefthandNav = web.Navigation.QuickLaunch;
    contextNavigation.Load(lefthandNav);
    contextNavigation.ExecuteQuery();
    NavigationNodeCreationInformation nodeToCreate = new NavigationNodeCreationInformation();
    NavigationNode navNode = lefthandNav[<num>];
    contextNavigation.Load(navNode);
    contextNavigation.ExecuteQuery();

    if (navNode.Title.ToLower().Contains(<value to check>))
    {
        nodeToCreate.PreviousNode = navNode;
        nodeToCreate.Title = navNode.Title;
        nodeToCreate.Url = <NewUrl>;
        nodeToCreate.IsExternal = <bool>;
        navIds.Add(navNode.Id); //For deleting the existing node after creating the new one
    }

    if (nodeToCreate.Title != "")
    {
        lefthandNav.Add(nodeToCreate);
    }
    //Use gist - https://gist.github.com/AsishP/70511f5eac4f069d8195ed36301758ab to delete
    contextNavigation.ExecuteQuery();
}