What is the root cause of gerd? if les is fixed( normal pressure) and still have gerd, how is that possible? i hear the term hyper acid sensitivity ?? is that even real, or a term that used when you dont know, but still reflux? short of breath?

There are multiple factors and different factors applicable to different extent in different people. Visit this site for information on this topic: https://www.mayoclinic.org/diseases-conditions/gerd/symptoms-causes/syc-20361940

Gravity never sleeps and OSA is common as is obesity in those with GERD. Discuss with your Dr if you can try elevating feet at head of bed 8 inches. You an buy blocks at Bed Bath and Beyond.