Dani, A Koncept could be a good choice for you. It is definitely more user freindly than the "full blown" race sails and as a sail that has been at the top of the speed table for many years it,s speed credentials cannot be questioned.
If you ask a question on the KA Forum or the "Ask KA" page on the website some of the team riders and ambassadors will be able to help you out.
http://www.windsurfing.kasail.com/forum/www.aus.kasail.com/personaladvice