Will anything happen to my kidney disease if I get in really good shape?

Probably improve but. It really depends on the nature of the disease and what you mean by get in really good shape. For instance some kidney scarring (fsgs) is related to obesity and gets better with weight loss. Also, excercise and wt loss improves blood pressure and diabetes stabilizing kidney disease. If you elaborate on the nature of kidney disease, it will be easier to tell you how to get in better shape for it.
No . Most intrinsic renal diseases are stabilized usually through healthy lifestyle.