Consultancy & Implementation for adding a chatbot to a website built with joomla

The website www.unternehmerzentrum.li needs a chatbot to offer assistant for the user (see an example in the attachment). The responsive website is built with Joomla.

These are the requirements and open questions:
1. The chat could be looked after by a person at least at the beginning
2. Can the chatbot learn from past chats and start answering on its own or is it only either automatically or manually?
3. Can the most frequent questions/answers be programmed so that the chatbot reacts automatically?
4. If the chat is looked after by a person, what happens if no one is there to answer?
5. The chat button should have a fixed position and should be seen on every page. It should also be responsive.
6. Which different implementations (plugins) would you suggest for this? And what are the features?

Later we would like the person who consulted us to implement the solution.

Timing: as soon as possible