They tell me ''disk access problem '' when i try to download...
someone know how change that ?

https://support.gog.com/hc/en-us/articles/115000014965-Installation-failed-disk-access-error

I don't understand cause Im on Norton and Gog.com is Allowed so i don't see where is the pb

You need to allow GOG Galaxy full access to your computer. Gog.com site alone is not enough. The easiest way is to disable your antivirus completely and make sure that you use an administrator account when trying to download. Alternatively you can use the offline installers. You can download them through your web browser. Just point your username which you can find on top of the site and from the drop down list choose "Games".

I have already deletemy Antivirus but how use a administrator account ? sorry for my english

??

Which version of Windows are you using? To check if you're logged in as an administrator select Start, choose Settings, click on Accounts. On the right side of the screen you can see your profile. If the sign below your username says Administrator, this means that you're logged as an administrator. If not select Start, click on your avatar, choose Log out and select the account which has administrator privileges.