
for cleaning, i use d/2 biological solution- it is recommended for old stones since its biodegradable and doesn’t have heavy acids. i usually wet the stone and scrub off whatever i can with a gentle bristle brush first THEN i use the d/2 and the stone usually brightens up on its own after a few weeks.
for leveling, it depends on the stone type and what kind of sinking it is. sometimes stones with a base will get it with the mower and get tilted. so i’ll use a crowbar and wooden block to get some leverage to shove it back (also do at the bottom) if the whole thing is sinking i will use a hoist / digging them out / laying a new slab for them & will stick special adhesive. i have stuff i hold the stone together with so it doesn’t get disturbed and can set properly