I have chronic lymphocytic leukemia. What can I do to fight against this disease?

Options available. There are a lot of treatment options available. However not everybody with cll need to get treated right away at the first initial diagnosis. There are some indications to start one on therapy. Nowadays, treatment is personalized and tailored to the biology of the cancer. There are some prognostic/predictive markers that can be tested to guide treatment selection, discuss with your oncologist.
Keep informed. New therapies are available for this disease. When to use these depends on your specific risk features (you will learn terms such as genetic risks for chr 17 or chr 11, cd 38 protein on the cell surface, mutation status of the cll cells) and requires an in-depth discussion with your doctor. Many options are available in addition to you ensuring you exercise regularly and have good nutrition.