Can i prevent diabetes if i have positive family history? i have normal body weight,normal waist circumference and i walk daily for almost 1.5 hours. i have decided to practice fasting aswell. will all of it help despite my positive family history?

The fact that you have family history of diabetes does not mean you going to have diabetes. It may be that you have a predisposition that is genetic. It is a good idea to have preventive habit and good you have started early; however it also not 100% guarantee. It is important not to be afraid and to have a lifelong habit of healthy nutrition with low carbs, more veg, fruits and regular exercises.