Use a Grout Remover compound from your local tile shop.
Laying tiles is easy, however, it is very difficult to do it correctly and get a good finish. It is best left to the experts
use some clean water in a bucket and add grout powder. Mix until even, like toothpaste. If it is runny, use more grout powder, if it’s too thick add more water.
Check to see if your tiler requires a license. https://www.licensedtrades.com.au/licensed/tilers
You can use a steam cleaner or a mixture of Baking soda and vinegar.
Clean floor. The first step is the most important
Prime the floor.
Fill cracks, floor, and wall junction with silicone. Also around fixtures and penetrations.
Apply a first coat of waterproofing.
Apply the second coat of waterproof membrane.
Keep the tiles in their original packaging.
Store the tiles off of the ground.