Clean black mold in my bathroom shower I can’t get rid of it ?

If it has gone through the grout or sealant the only thing to do is remove and thoroughly clean then replace. If it has gone through the actual backing of the wall it means a bigger job, but hopefully this is the answer. The last resort to try cleaning for black mold is bleach unfortunately so I hope it has not gone further for you. No bleach if you are on a septic tank though. regards and good luck.

Have you checked for a leak behind the walls? It can take a year for a slow leak to become fully apparent.

Otherwise, try spraying bleach on the area, followed by vinegar. Rinse and dry completely. Regrout if needed with a very good acrylic grout.

Always run the shower exhaust fan during showers and for at least 20 min. after showers. Squeegee walls of all water and dry all surfaces with a microfiber towel.

Use a mixture of household bleach and hot water in a spray bottle. Let set for awhile, then wipe off with a dry rag. You need to be very careful as the mold spores can become airborn, so wear a mask and disposable gloves and dispose of all in a bag in the garbage. Also, check your ventilation fan to make sure it is working.

You need to find the source and solve it. Bleach and water will clean the mold. Vinegar and water will kill the mold spors. If the mold comes back you have a problem within the walls. Make sure you have an exhaust fan to expel moist air out of the bathroom.