Will all be in the testing
Acquire a suitable tile stripping agent , just a 1 litre
Start with working on two tiles only in a discreet area ,
Apply generously and work for 10-15 mins with a stiff brush or as stated
Scrub every 1-2 mins do not let it dry out, add more product if it thickens while scrubbing.
Rinse and repeat if the paint is not fully removed.
If this works, use the rest of the one litre and this will give you the amount you need per Sqm per litre .
If this is something like red cardinal paint ( good luck) don't be supprised if you only get 1-2 Sqm per lit , can be an expensive ,but worth it if the tiles are in good condition.
If you strip the whole floor, most important , drying times - mine 7-12 days or until fully dry ,dependant on moisture.
After this there are plenty of options for sealing
Oils and wax or more modern emulsions with easier maintenance.
Photos would be great .