La grade b reflux esophagitis and erythematous mucosa in the atrum is what i have. i just simple want to know what causes it?

Reflux esophagitis: simply put: the contents of the stomach, mainly acid, stayed for a long time outside of the stomach up in the esophagus where they shouldn't be, causing inflammation of the lining of the esophagus hence the term, and that what causes heart burn and other symptoms. As for the causes for the reflux itself, they are numerous, most common are diet (e.g. fat, caffeine,) being overweight, drugs, etc..