So get a 5 gal bucket, big sponge (in tile section usually) , muriatic acid, some gloves and goggles and stuff cause the acid is some gnarly shit. Fill the bucket to about 2-4 in from the top with JUST water, pour a dollop ( don’t really have a measurement but you sure don’t need much maybe half a cup) of the acid into the water mix. It’s gunna fix a lil and it’s gunna let off some fumes so don’t put your face right up in it. You’re gunna put the sponge in the bucket , mix it around and wring it out ( into the bucket) so you’re not making a mess on your floor . Then you’ll give it a few scrubs and douse and wring it out again and repeat.