Fast breathing associated with cough and crepitations,what is the most likely diagnosis?

The most likely diagnosis in this case would be pneumonia. Pneumonia is an infection that causes inflammation in the air sacs in one or both lungs, leading to symptoms such as cough, fast breathing, and crepitations (crackling sounds in the lungs). It is important to seek medical attention if you are experiencing these symptoms, as pneumonia can be a serious condition that requires treatment with antibiotics.

Pulmonary edema