What is the condition in which the heart does not pump blood as well as it should and blood and fluid back up into the lungs?

The answer here is Congestive Heart Failure (CHF).

CHF occurs as a result of the weakening or stiffness of the heart muscle. Health conditions such as coronary artery disease and hypertension or high blood pressure can contribute to the deformation of the heart muscle. While not all conditions of CHF can be reversed, there are treatments and daily lifestyle changes (e.g exercise, consumption of healthier diet, reduction of sodium intake and maintaining a low stress level) that can improve symptoms of CHF.