If i have a main menu and a first level for game i need a script to pass from main menu to my game ?

How i can realize a tranzition between main menu and the game stage ?

If you have a scene for your MainMenu and a scene for your game, you need to add the scenes to build settings : File → Build Settings → Add Open scene (add the two).

after in your code : SceneManager.LoadScene (“OtherSceneName”);

that’s all