Dear Silvana:
I do try to help out DIYers in any possible way, but this is beyond any DIYer ability. As a professional the only advice that I can give you is to get professional help. It will cost you more than if you had the tiles installed by a proficient tile setter, but at least your floor will not be ruined for good.
I consider stone floor grinding and refinishing as the very pinnacle of all activities related to stone. You can't even set tiles right; how can you even hope can you hope to be able to rectify your installation job? It takes special equipment, special abrasive means, and, above all, knowing what you're doing.
Sorry to be so blunt, but this is the best piece of advice that I can give you and, I assure you, you will be sorry if you won't follow it.
May I ask you now to please read and e-sign our Statement of Purpose at: http://www.marblecleaning.org/purpose.htm?
Ciao and good luck,
Maurizio Bertoli
Article ID: 1415
Created On: Fri, May 9, 2008 at 12:08 AM
Last Updated On: Fri, May 9, 2008 at 12:00 AM
Authored by: Maurizio Bertoli [mail@mbstone.com]
Online URL: https://marblecleaning.org/knowledgebase/article.php?id=1415