As @JLeslie just wrote, a fridge works best when there is something inside it other than air. Otherwise, there is not much inside it to cool, other than the air (which mostly leaves when you open the door), and the inner walls of the fridge, and the shelves (which are usually pretty light, so don’t do much to cool anything down).
So if you have almost no food, put something in it that it can cool down, that will help it cool other things down that you want to be cold. Such as, a few large containers of water, until you get some food in there.
Otherwise, if you start with an empty fridge, the first few things you put in it may not get cold very fast. Especially if you keep opening the door to check on it.
@Tropical_Willie Sorry, but your comment about a fridge being replaced after five years . . . makes me want capitalist humanity to all die immediately . . . (I mean, we (or at least, our capitalist excesses) deserve to go extinct for our selfish closed-minded stupidity about such things as built-in obsolescence and destroying our own planet, but the rest of the species don’t deserve to go extinct . . . and nor do the humans who aren’t like that, but if we can’t stop them, maybe we deserve it too.)
What the &@%#? Why?
BTW, in my family, we NEVER replace refrigerators unless/until they have some major breakdown. Like, 40 years later, still working.