Need help with understanding Whatsapp Api

I am looking for a freelancer who has had some experience working with the Whatsapp Business API. What I am needing is help in guiding me through the process of setup and use. Some questions that I'd like to know:
- What is the process of applying? What requirements are needed? How long does it usually take? Is there a cost?
- Once approved, how do you begin using it? How do you program triggers and auto messages?
- What tools should I combine it with to get maximum effect? Can I have multiple agents replying?
- How does multi-language apply? Do I need different IDs for this?
Please send experience working with this or similar projects with your bid.

Thanks