Many things can cause the reflux from eating too much volume to problems with the surgery itself. Follow up with your bariatric surgeon for an evaluation. If it continues then see a gastroenterologist.

Same process as before a bypass. Stomach acid will enter the esophagus if there is weakness in the lower esophageal sphincter. However, after a bypass, there is very little stomach remaining in continuity with the esophagus, so acid production will be less. Most bypass patients do not get a lot of acid reflux.