I feel like a sort of expert on reflux, because I cause it all the time (a chef's curse).
The natural sequence is long term reflux leads to Barrett's Esophagus (raw, eroded spots), which can lead to esophageal cancer untreated.
So once you get diagnosed, you probably have to watch and control your stomach acidic levels in general, mostly through medication. Omeprazole and similar. These meds aren't meant to be taken for more than a few weeks but for people with serious reflux, it's not a choice. But these are over the counter meds, $$ but easy to pick up.
It's doubtful you can fully solve the issue with just diet changes, but knowing "triggers" and avoiding or dealing with them is key. For example one of the worst is tomato sauce. If you're gonna have Italian, pop an Omeprazole the morning before. It takes a couple days to work but it nips almost any food-related GERD.
Soda, alcohol, greasy food, spicy stuff, all common triggers for people.
Reactively, you have various options. People diss on Tums but as long as you don't overdo them, they work. Or a spoonful of baking soda in a full glass of water. Drink, burp, Instant karma.
Just don't overdo it. Tums have a limit of like 4-6 per day, but if you are doing that daily, you probably want to take a daily med instead. Talk to your GI first obviously. You don't want to take those OTC meds regularly unless you are at the "do I want cancer or just an overmedicated kidney" stage.
Some foods that always help: anything relatively neutral or alkaline in pH.
My personal go to for GERD: Keep a nice stock of celery sticks. Most veggies are alkaline, but celery is full of water and won't make you gassy or bloated (which is why it's often served with buffalo wings).
Milk, lactose free or not, is a fast acting remedy for most people because of how it coats the stomach lining (also why it's often served as an antidote for ultra spicy foods like Carolina Reaper sauce).
It goes by many names: indigestion, heartburn, acid reflux, GERD. Whatever you call it, it happens when stomach juices flow in the wrong direction, back toward your throat. Find out from this WebMD slideshow which foods may help with it.
www.webmd.com
Also, make sure you sleep with your head elevated with pillows or an adjustable frame. The worst damage from reflux comes during overnight sleep while you are lying down.