Grandpa has bladder cancer and CLL leukemia. What causes these? So I know what to do to avoid ever developing either of these

Preventention of Can. Cancer is primarily a disease of the older age groups (>65 year olds). From that perspective you are too young to worry about it. yet there are precautions you can/should take to reduce your risk of developing cancer. This requires you to live a Healthy lifestyle, meaning a healthy Diet(ample vegies and fruits) and regular exercise so that your weight is normal; stay away from Smoking and alcohol.