Admin Menu for New Post

It looks like you’re trying to add a custom post type called Tutorial. WordPress handles creating the menu all on its own – all you need to do is register the post type. You can start with something like:

// Use the `init` hook.
add_action( 'init', 'wpse_412823_register_tutorials' );

function wpse_412823_register_tutorials() {
     // Set up arguments for the post type.
     $args = array(
          // There are many arguments, but this will make a bare-minimum post type.
          'public' => true,
          'label'  => 'Tutorials',
     // Finally, register the post type.
     register_post_type( 'tutorial', $args );

You will probably want to add more $args to fine-tune things, but just registering your custom post type will give you all sorts of built-in functionality like adding the admin menu item.