I'm a 13 year old girl that weighs about 55kg and is tall 1m 50 cm.. I want to loose weight and reach the 40-45 kg till summer. Can I make it ? If yes,how?and please sugest me some ways of how I can exersice for flat belly and stomach

That much weight loss for a 13 year old girl is not healthy. You are still growing, and should not lose a lot of weight at this stage.

You can get a lot healthier, and look a whole lot better by improving your food choices. Cut out fast food, anything deep fried, anything with sugar or white flour, and instead eating more protein, healthy fats and lots and lots of green vegetables.

Get plenty of exercise. Walk as much as possible, cycle if you have a bike, dance and swim and jump rope. Watch less television and go to bed earlier.