Hello and welcome to HealingWell. My heart goes out to you as I know how awful it feels to fear something happening to your Father. Big breath.
You can't reverse many conditions that lead to heart failure, but heart failure can often be treated with good results. Medications can improve the signs and symptoms of heart failure. Lifestyle changes, such as exercising, reducing the salt in your diet, managing stress, treating depression, and especially losing excess weight, can improve your quality of life.
Heart failure is a chronic disease needing lifelong management. However, with treatment, signs and symptoms of heart failure can improve and the heart sometimes becomes stronger. Doctors sometimes can correct heart failure by treating the underlying cause. For example, repairing a heart valve.
Make sure you Dad sees his cardiologist regularly and perhaps you can help him with some lifestyle changes.