How to get the ID of a Telegram channel, chat, user or bot?
https://rapidapi.com/i-YqErDdkq0t/api/telegram92/tutorials/how-to-get-the-id-of-a-telegram-channel,-chat,-user-or-bot%3F

We recommend using username-based queries. In the case where there is no username, you can use a query by ID. As a reminder, channel and chat IDs are negative, while user and bot IDs are positive.