Help, how much calories should i have everyday to lose weight or maintain and not gain?

Depends: First, it depends on your size, your daily physical activity, and your weight. Second, not all calories are the same. Some calories are more highly absorbed by the body than others. Instead of worrying about calories try to eat only healthy foods as i did. I lost 25 pounds without counting a calorie by simply eliminating foods that don't promote health such as processed and fried foods..