HG Shine Restoring Tile Cleaner
Dissolve 50 ml in half a bucket (5 l) of lukewarm water. Then clean the floor with a wrung-out mop or floor cloth, regularly rinsing it in the cleaning solution. Do not rinse or mop dry, simply leave the floor to dry on its own. 1 litre is sufficient for 20 washes, so it's very affordable too!