In the first photo you will see a brown plastic disc insert at waist level. This should have a self tapping screw through it that holds the kitchen cabinet to the steel space frame of your Eriba. The fridge is in turn fitted to the cabinet.
The cover to this insert is missing. I am also guessing the screw may have worked loose and as such your cabinet is free to move.
Using the weight of your body push the cabinet back to the wall and refit a/the screw. If the screw does not bite, then go up a gauge and you could squirt some liquid nails mastic into the steel framework hole. Whilst you are at it, check the other cabinet fixings including those that may be inside.
Colin