“Does gastritis go away on its own?”

Depends on the cause. If it's from infection like H. pylori, then yes, it will improve after you treat the infection. But a lot of gastritis found is nonspecific with no clear cause and that type doesn't go away. Last point is that most chronic gastritis doesn't cause symptoms. Look for other explanations rather than blaming gastritis for pain, bloating, burping, heartburn, etc.

Gastritis is a biopsy proven diagnosis. Many people have gastritis. The acid in the stomach causes inflammation of the stomach. There is nothing to worry about gastritis unless you develop erosive gastritis or ulcer.

If it is due to dietary irritants, then you need to change your diet first. If it comes from an infection, then you need antibiotics. Other causes will need specific treatment.