images dont work. Anyways: you dont install a hook IN the hole where the cables come out - you drill a hole next to it and fix a screw with a hook top in a dowel. Pretty sure you will find some youtube videos on that for the millenials...
The junction box seems to be plastic, so screwing to it directly may be risky, considering the lamp is about 2kg (don’t know how flimsy that box is). If it’s not plastic, you can screw directly onto it. Other options:
1) seeing as the lamp has a nice, big baseplate, you can install a little mounting bracket (Deckenleuchte or Deckenlampe Halterung in German), screwing to either side of the box, or
2) with or without a mounting bracket, set a small plastic anchor (such as a Hilti HUD, or a Fischer Duopower) either 6mm or 8mm through either large hole at the end of the junction box, and screw your hook into it (Schraubhaken in German).