PiranhaCMS/Piranha

Hello guys, i am looking forward to start using Piranha CMS but i am struggling with basics. Could one of you please help me with this issue? I´ve created new project from template and also created new empty module from template. I´ve tried to implement that module into my site like this:

using Microsoft.EntityFrameworkCore;
using Piranha;
using Piranha.AttributeBuilder;
using Piranha.AspNetCore.Identity.SQLServer;
using Piranha.Data.EF.SQLServer;
using Piranha.Manager.Editor;

var builder = WebApplication.CreateBuilder(args);

builder.AddPiranha(options =>
{
    /**
     * This will enable automatic reload of .cshtml
     * without restarting the application. However since
     * this adds a slight overhead it should not be
     * enabled in production.
     */
    options.AddRazorRuntimeCompilation = true;

    options.UseCms();
    options.UseManager();

    options.UseFileStorage(naming: Piranha.Local.FileStorageNaming.UniqueFolderNames);
    options.UseImageSharp();
    options.UseTinyMCE();
    options.UseMemoryCache();

    options.UseReservationModule();

    var connectionString = builder.Configuration.GetConnectionString("piranha");
    options.UseEF<SQLServerDb>(db => db.UseSqlServer(connectionString));
    options.UseIdentityWithSeed<IdentitySQLServerDb>(db => db.UseSqlServer(connectionString));

    /**
     * Here you can configure the different permissions
     * that you want to use for securing content in the
     * application.
    options.UseSecurity(o =>
    {
        o.UsePermission("WebUser", "Web User");
    });
     */

    /**
     * Here you can specify the login url for the front end
     * application. This does not affect the login url of
     * the manager interface.
    options.LoginUrl = "login";
     */
});

var app = builder.Build();

if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}

app.UsePiranha(options =>
{
    // Initialize Piranha
    App.Init(options.Api);

    // Build content types
    new ContentTypeBuilder(options.Api)
        .AddAssembly(typeof(Program).Assembly)
        .Build()
        .DeleteOrphans();

    // Configure Tiny MCE
    EditorConfig.FromFile("editorconfig.json");

    options.UseManager();
    options.UseTinyMCE();
    options.UseIdentity();
});

app.Run();

line 28 to be exact. I´m able to see module in the manager under Modules tab. But there is this inside Module´s Init() function:

// Add manager menu items
            Menu.Items.Add(new MenuItem
            {
                InternalId = "ReservationModule",
                Name = "ReservationModule",
                Css = "fas fa-box"
            });
            Menu.Items["ReservationModule"].Items.Add(new MenuItem
            {
                InternalId = "ReservationModuleStart",
                Name = "Module Start",
                Route = "~/manager/reservationmodule",
                Policy = Permissions.ReservationModule,
                Css = "fas fa-box"
            });

But there are no new Menu items in the manager.

I´ll be more than happy to provide any more info. Thanks in advance for any help. :)