Best Tile Floor Cleaner

I have a house in 1942 with original black and white (marble?) From tile in the bathroom. I tried scrubbing, but it did not help? Should I use some grout cleaner, bleach, acid? to help clean tile and grout?
Also, I'm so attached?

use oxy clean on the great work grout then seal the grout

the tiles need a scum for the grout with bleach and / or Regout it then seal it. acid burns and is not the right product. experinment with different tile cleaners and see what works. also contact your local dealer marble and ask their advice for marble Convection

I suggest !!!!! superheated steam clean

an Italian brand (forgot the name) is awesome suction cleaners that clean without any chemicals.

I used to clean a hotel with a vintage, amazing and easy ... do not rub hard or harmful chemicals. and 1 liter of H20 gives you 10,000 liters of super heated steam.

Its environment too