If ever among you there are some who have faced this problem and solved it, it'll be okay that you call the walkthrough on the rockstar site or otherwise. In any case I will.
Ps: if the game will work I will change my review.
[EDIT]: I solved my problem ... First, I downloaded a file named "GTA5FileCheck_SHA1" ... FYI, this is a small program (GERMAN but very simple to understand) that checks if all files in the game folder are good or corrupt.
So I started this software (ESPECIALLY ADMINISTRATOR) and it turned out that I was 5 corrupted files. I have deleted the game folder, and then I restarted the game from the desktop shortcut ... And, the launcher appears and starts downloading (a 20 ene minutes for me) these missing files. Once finished downloading, I could play, and frankly .... I gets off !!!!!!