What Can I Do to Avoid a Plateau in My Weight Loss?

There is no magic when it comes to losing weight. A high initial weight loss (eg 9Kg in 5 weeks) is due to a loss of about 5Kg of body tissue (mostly fat) and 4kg of body water. You lose the water because the glycogen that your body uses as an energy supply in the early days of a diet also holds water. When that glycogen is replaced water is regained. This is when you might experience a "plateau".
The reality of weight loss is that it is only possible to lose about 0.5 - 1kg of body tissue per week. If you stick with a weight loss plan of about 1000 Calories per day, and persist through the plateaux, your weight loss will resume.