Example script for Google Scripts, to send messages to your Telegram bot.
The script replies to you with your own message, sticker or image. If you try to send another thing it will send "Try another stuff".
Copy the file main.gs in a Google Drive script and publish it as an app (execute as Me and give access to anybody even anonymous).
You will need to create your bot with Botfather in Telegram, take the API key and replace it in main.gs where it says YOUR-API-HERE.
Oh and remember to create a webhook first in Telegram with the URL of your Google Script.