I have curved fingernails like cat's claws and clubbed tips. the middle and ring fingernails also twist when long enough why is this?

Clubbed Fingers: Clubbed fingers is a symptom of disease, often of the heart or lungs which cause chronically low blood levels of oxygen. Diseases which cause malabsorption, such as cystic fibrosis or celiac disease can also cause clubbing. See your doctor.

Fingernail issues: All fingernails tend to curve somewhat when they are long enough. Without seeing how bad yours are, is hard to tell whether they are outside of "normal". I am not sure what makes you want to have long fingernails, but if they are normal length (within your fingertips), they should not curve.