I suffer from gastritis, thus it is not chronical, I would like to know which food I should avoid?

Gastritis. Diet depends on what is the cause of gastritis. Gastritis is not normal and you should see your doctor for an examination to determine the cause and then treat the cause. E.G. An infection with h. Pylori can cause gastritis and be cured with antibiotics. You must find the cause.
Coffee/tomato/spicy. Foods that are acidic in nature. The worst foods are coffee/ tomato based foods (pizza, pasta), spicy foods and acidic foods (orange juice), and smoking tobacco can all exacerbate your gastritis and foods to avoid.