“Can bad hearing be fixed?”

Removing earwax. Earwax blockage is a cause of hearing loss that can be fixed. A health care provider might remove earwax using suction or a small tool with a loop on the end.
Surgery. Some types of hearing loss can be treated with surgery. For repeated infections that cause fluid in the ear, a care provider might put in small tubes that help ears drain.
Hearing aids. If hearing loss is from damage to the inner ear, a hearing aid can be helpful. A hearing specialist, known as an audiologist, can talk about how hearing aids can help and what kinds there are. Audiologists also can fit you with a hearing aid.
Cochlear implants. When a regular hearing aid isn't likely to help much, a cochlear implant might be an option. A cochlear implant isn't like a hearing aid that makes sound stronger and directs it into the ear canal. Instead, a cochlear implant goes around the parts of the inner ear that don't work to spur the hearing nerve.

Works Cited:
https://www.mayoclinic.org/diseases-conditions/hearing-loss/diagnosis-treatment/drc-20373077