Where is mine? Only appears the installer for Hellraid DLC

If you are using Galaxy, all Offline installers show in the Extras section of the game.
Scroll down a bit, it's the one with 25 GB download size named "Dying Light - The Following: Enhanced Edition".

If you are using the web site, it's the first 8 links in the "Dying Light - The Following: Enhanced Edition" section.

I check the web and it's there. Why doesn't it appear in gog galaxy?

Id does for me. Most likely it's just a sync problem and wil be resolved automatically soon (I don'T know if there's an option to force synchronization). Otherwise you might want to contact support.
After all, afaik Galaxy is still beta.

The "extras" list is filtered by the download language selected, if you change it to "English" you can see the full list.

I have the same problem

Der Fehler liegt an der Voreinstellung der Bibliothek für die Downloadkarten, d.h. es ist eine andere Sprache aktiv (und nicht English). Die Voreinstellung für die Bibliothek kann in der Karte von Dying Light nicht geändert werden. Dort gibt es nur English.

Lösung: In einer Karte eines anderen Spiels mit mehrsprachigen Downloadmöglichkeiten auf die Sprache English umstellen. Anschließend die Downloadkarte von Dying Light wieder öffnen. Jetzt sollten alle Downloads wieder vorhanden sein.

Go..gle translate:
The error is due to the default setting of the library for the download cards, i.e. another language is active (and not English). The library preset cannot be changed in the Dying Light map. There is only English there.

Solution: Switch to English in a map of another game with multilingual download options. Then open the Dying Light download card again. All downloads should now be available again.