Welcome to HCM
Your father is having hiatus hernia
,it is of two types1)Sliding Oesophageal Hiatus hernia 2) Para Oesophageal Hiatus hernia.
Large and long standing hernia can cause GORD ( Gastro Oesophageal Reflux) in which acidic content are regurgitated in Oesophagus and can cause vomiting
,heart burn, some times cgest pain.
Treatment consist of acid reduction in stomach and prevent any regurgitation.
You should consult a good Gastroenterologist if it is sliding type it can be treated and other type para Oesophageal one sometimes gets strangulated and bleeding can occur and needs surgical corection.
So management depend on exactly which type of Hiatus hernia he is having .
Hope this information helps you .
Good luck to you.