Unkalibriert: So you have the retail version that needs the first patch to run, correct?
First you have to redeem your game code here:
http://www.gog.com/redeem After that you should have
The Witcher 3: Wild Hunt in your library which is accessible on the top of the page, but you may have to log in first, though.
After logging in, click on "account" which should bring up the library.
When you click on the game's name it should prompt the downloadable files, from which you need the "patch 1.01/1.02" for playing the game. That should be about 300 megabyte... wait a moment... where is the 1.01 patch? Its gone...
Seriously, gog? Shouldn't the retail costumers still get their 1.01 patch? oO
As far as I know the game itself downloads patch 1.01/1.02. For this you don't need to redeem the code. But you should redeem it for later patches and DLCs.