My 91 yr old dad has fluid on lungs. he had a stroke affecting his swallowing. wat happens if the fluid carries on goin on to his lungs?

Different problems: "fluid on lungs" usually refers to congestion of the lungs and/or fluid around the lungs. This is not caused by difficulty swallowing. People who have difficulty swallowing and aspirate liquids or food may develop pneumonia.

Aspiration PNA: I have a different opinion. Stroke leading to dysphagia (difficulty swallowing) can cause accidental aspiration of one's own saliva & secretions, which can perpetuate fluid accumulation in the lungs. Along with acute treatment for aspiration pneumonitis, your father should get swallow rehab to prevent future aspiration. Good luck to him!