Is there a cure for kidney malfunction?

Loaded question. : Many things can cause kidney damage including drugs, infections, shock, medical illnesses, and more. Sometimes the injury is reversible and sometimes it is irreversible. Some causes can be "cured" with specific treatments while other causes of kidney dysfunction can only be managed optimally. Sometimes there is no cure and renal replacement therapy options must be considered. Hope this helps.

Depends: If the damage is temporary, what is termed "acute renal failure" then it is usually gets better. However, if there is continual insult to the kidneys then they may take more time to recover. The top killer of kidneys are diabetes and hypertension. It is very important that if you have these, then they must be controlled. I also see a lot of damage done from nsaids. Take these sparingly.