Drupal 8 - Hello World Module

hello_world.info.yml

name: Hello World
type: module
description: Say Hello World
package: Custom
core: 8.x

hello_world.routing.yml

hello_world:
    path: /hello/world
    defaults:
        _controller: Drupal\hello_world\Controller\HelloWorldController::hello
    requirements:
        _permission: 'access content'

src\Controller\HelloWorldController.php

<?php

namespace Drupal\hello_world\Controller;

class HelloWorldController {
    public function hello() {
        return array(
                '#title' => 'Hello World!',
                '#markup' => 'Here is some content.',
            );
    }
}

I have to create a custom module for an event section with the following features:
a. The ability for Admin to create Event and Event Categories.
b. Front end – List all events, grouped by category.
c. The ability to subscribe to the event. All event subscribers should be stored in DB and
listed to the Admin.

I have created a module which create a custom content type names Event Detail + a txonomy Event Categories

Can i have your whatsapp number?