I bought this cactus a few years ago and I want to fix it. I don’t know how to fix the almost translucent spots it has and I would like to repot it but not sure how since the rocks are like glued in?? Any tips would be really helpful
If I was doing this, I'd lay the whole thing down on a newspaper. Then squeeze the pot, moving around the pot. You're trying to loosen the soil. Then use a pencil of something and try to push through the bottom to pop the soil, roots and rocks out of the pot.
Then try to flex or snap off the rocks. You don't need to break up all the rocks, just split them where the stems are. I don't think hammering on the rocks with the plants in the pot is the best tactic.
Next remove any soil, hopefully yours isn't too compacted. Remove any dead roots and snip any really long ones. Then repot using cactus soil. I would plant them separately. The two tall ones will want to spread and fill a pot. The shorter one is going to grow as a column and doesn't need a wide pot. Be sure there are holes in the bottom of the pot. You can use small pebbles as top dressing, just don't glue them down.
Depending on where you are, you should let the repotted plants rest for a few days before watering lightly.
Note that the dots on the tallest plant are glochids, tiny barbed spines that are annoying/painful. Use some folded newspaper to handle that one. You can also use tongs or large tweezers.
Not sure what the problem with the fairy castles is (the middle-sized one with the lighter green spots). It appears to be making new offsets, which is a good sign. As a precaution you should remove one or two of the offsets and root them in small pots in case the main plant is sicker than it looks in the picture.
Close up pictures of the bad parts may provide more clues.
You probably need to break them out of the "glued in" stones (carefully with a hammer? screw driver?), and then repot them in some decent potting mix. The plants look like they would respond to new soil and sufficient light and water. You could repot them together or individually. Below is a helpful link with general cactus care information.