here there's a link for the day 1 patch, my question is , will gog galaxy automatic download it or ill have to do it manually? http://play.thewitcher.com/

if you have "Auto-Updating" enabled for the Witcher 3 in the Galaxy client then yes the day 1 patch will automatically download when it is available.

If you scroll down on the site you linked & read the text in the green box you will notice this line
"Automatic updates - all future game updates delivered automatically"
which answers you question :)