Someone tell me about gog.com and i purchased witcher 3 free one and i successfully older and get email also .but how i download now i install galaxy 2.0 software in there i search of witcher 3 it say to gift as you owned this .where is installer how to download

You don´t need to install galaxy if you don´t want. Go to your account through the web and click on your library (not in your profile, just down where puts games), and click in the game, here you will see the download files to install the game.

Just hover with the mouse over your account name and then a top down menu pops up. There should be an entry called "games", click on it and then it should take you to your library, whre all your games are. There you can choose the game you want to download and click on the download link(s).

If you actually want to download the offline installer from within Galaxy 2.0: Click on the game, then "Extras" (top-middle of the screen).