When we eat fruits before food or after food.

Both! I've not read any studies that suggest that timing of fruit consumption makes a difference relative to your non-fruit intake. In other words, enjoy your fruit w/o worrying about when you eat, assuming that it doesn't affect your normal appetite. Strive for 5 servings of fruit plus an additional 5 servings of veggies each day. Try not to count store bought juices as you're missing fiber content.