How do i restore scratched and scuffed marble tiles and marble slab?

Lithofin do a product called Lithofin MMP (Marble Polishing Powder - which is oxalic acid based). It is a professional product and maybe hard for a DIY'er to get hold of much less use correctly. I would suggest using a proper stone restoration company for the best results. Once restored I would use the correct sealant and maintenance product regularly. If it is close to outside access I'd also put mats down to catch any grit etc which will obviously do the floor no good at all.