Hey guys!
I want that when a user starts a conversation in whatsapp (saying their email) it finds in a google sheet a parameter and send them a whatsapp message with that information. I want to do it with Wati.
Somebody can help me?
Suggest you do Make Academy and all the steps will be taught. You can translate those to your specific use case.
The knowledge is out there, but it is best found by learning the structure.
As a shortcut, search in the community here but honestly you will have better control if you actually do the exercises in Make Academy. You need to grasp the fundamentals so you can troubleshoot issues…and avoid a bad trigger sending multiple messages! 
I started a month ago and have learnt a lot.
Best of luck. 
PS check the guide on Wati itself. I did not know about them, but perhaps this will help: Wati and Make