The high-gloss finish works to your disadvantage as you polish. The higher the gloss, the more light reflects off at a different angle from imperfections. This is why you now see the scratches in your marble fl
First, remove any jagged edges and bumps using an angle grinder. You can then finish the surface using an industrial rock polisher (provided by thegeological survey) or an orbital palm sander. Polishing stone is similar to sanding wood, however you will need to use sandpaper / grit that is ...