Telegram Bot Development with API Integration

I am in need of a competent developer who can help me assist with a Telegram bot. The bot will interact with some information API and paid users can use it only, along with another external API. It will require some customization, including custom command integration, database integration, and user authentication. These custom commands need to be able to execute a few functions such as:

- Sending automated messages
- Fetching data from external sources as pdf or images
- Performing calculations

The ideal candidate for this job possesses in-depth knowledge and experience in Telegram bot creation, database management, and API integration. Familiarity with user authentication mechanisms is a must.