HOW FIX AND SOFTEN A SHADE?

graphic attached:  https://we.tl/mp1QQUTUSJ

Maybe if I can upload and share file could you help me?

I am not sure how this thread got so far down the page unanswered!

Make a selection of the marble.  The Pen tool would be best, but use the Lasso tool if you are more comfortable with it.

If you used the Pen tool, make the path a selection (Red arrow) and copy to a new layer.

Make the path a selection again, and add a layer mask to the copied layer (Green arrow).

Unlink the layer mask by clicking on the chain icon (Cyan arrow)  Note it is already turned off in my screen shot.

Use Free Transform (Ctrl t) and drag up the copied marble so that the current shadow is hidden behind the layer mask.

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Add a new layer, and paint a full hard black brush stroke across the screen.  Touch down at one end.  Hold down the shift key and touch down at the other end.

Repeat the previous steps to add a layer mask to the bush stroke, and unlink the layer mask

Make sure you have the layer, and not the layer mask selected (of the black line layer), and apply Gaussian blur.  I used a value of 10.

Reduce the layer opacity to suite.  Mine is set to 25%

Move the black line up or down to position it where you want it. (Note:  with the layer mask unlinked, the line will only show below the grey bezel.

I think you only asked about the lighter coloured marble.  The reddish marble above the bezel is more complicated, but I'll post this and cover that in a new post.  Note I have not worked out how to do it yet :-(