Thought this would be a good read for you @Alain2 (http://nbcba.org/forum/index.php?action=profile;u=2146) or anyone else just starting. I wouldn't worry too much about water chemistry since you're just starting (unless you're really interested) Most prople dont start adjusting it right away, they get the basics down first.
http://www.themadfermentationist.com/2015/11/design-beer-recipe-in-10-steps.html