Is eating nestle cornflakes without milk for breakfast and fruits for lunch and dinner good for losing weight?

It's terrible! You need protein, especially for breakfast. Ya like oatmeal ? It'd be a huge improvement! If not, at least put milk on your cereal, at least you'll get some real calories. Fruits are sides or snacks, not meal replacments, again protien is needed, along with fat, we are complex creatures, not just calorie banks, if your diet doesn't provide enough baseline nutrients, it will give you the reverse of which you seek, you will lose muscle, your brain will tell the body to start storing more calories, and your mood, sleep, energy will all suffer. It's not rocket science, enjoyable exercise and a diet that supports it and you. Something you can make a lifestyle and stay with for life ( after a few months, you'll never want to quit, as long as you keep it enjoyable and sensible!)