"Dish" and "meal" respectively "plat" and "repas" are not synonyms. While "dish" is just one plate of prepared food - let's say Bratwurst with Sauerkraut and Kartoffeln (to stay in the context) or think of "le plat de jour" also, the term "meal" means something larger like a composition or whole sequence of different dishes: Soup, starter, main dish/course, salad, side dish, dessert, etc.
See for meal: https://en.wikipedia.org/wiki/Meal
See for repas: https://fr.wikipedia.org/wiki/Repas
See for dish: https://en.wikipedia.org/wiki/Dish_(food)
See for plat: https://fr.wikipedia.org/wiki/Plat