You have on the fruit the white and you have the dark, your shadow is correctly even darker. The two mid tones are not very clear and too close. Try with a kneaded eraser to lighter the area around the very white stuff. And when you use pencil strokes, try and use them lightly and in the direction of the shape. Yours are mostly horizontal diagonally and they take away from the fact that the mandarins are rounded. If you use curved soft strokes you emphasize the form of the shape. If you do it all well you should barely see the lines but if you do, it is better if they help the shape.