Creating a chatbot in Telegram is very easy, since it allows polling in order to to receive messages, it doesn’t required a callback url and a https certificate (like Facebook Messenger)
Telegram is really coherent and you have to use a chat bot to create a chatbot. Connect to @BotFather and type /newbot, then in the next two steps give the bot a name and username (this will be the real unique address of your chatbot), you’ll get something like this for @my_new_chat_bot

Telegram create chatbot
Copy and paste the access token. For more information read here. Then open your Node-RED and add a Telegram Receiver node , in the configuration panel, add a new bot and paste the token

Paste Telegram token
Telegram Receiver node also support the connection with web hook, the URL must be secure (https) and should hit the /redbot/telegram endpoint of the Node-RED instance, for example
<https://a.secure.url.com/redbot/telegram>
Use ngrok to test the webhook locally during development.
Telegram Receiver node and Telegram Sender node have a double bot configuration for development and production. By default is used the development configuration. To use production configuration, edit Node-RED settings file (settings.js) and set the environment global variable to “production”. See Deploying RedBot for more details.