Your atempt could be realistic as long you are making a seamless difusse gray background.
Seamless is a roll of paper that you do not fold so you have a curved background.
In order to make a floor separated from the wall you need to put a clear seam (A)
But you have another problem, you are making a "curved gradient" (B). Make a straight one (C)
But if you want other features, like a reflective one, you need to actually have SOMETHING to reflect (D).
Ia am not sure if you want a dark background or a white one. I'll change it to white.
But also in your target image you have a celling... did you noticed that?
The idea of the gradients come with this logic: The lights are on the celling pointing down, so you have more light on the floor. (E)
Some of this light is reflected to the wall (F) and less back to the celling (G)
Also, a background is diferent from a room... A room has perspective given by the walls (H) and its respective reflection (I)
But there is an aditional effect on your second image. It is a 3D render with one thing called Ambient Oclussion. This is in the corners that are more "hidden" there is a shadow. This zone is most likely to be in shade.
So in the image you see this "shadow"... ambient oclussion (J).