If you can learn to do a 10 day fast, you can do anything. A series of 7 - 10 day fasts is just as good as a series of 40 day fasts for weight loss, because you have to refeed for equal periods anyway, so it takes the same time for weight loss.
No matter how hard you try, this will take time, weight takes years to put on and it can't be taken off overnight. However, as you progress you will feel fitter, healthier, more motivated.
I wish you every success on your first fast, but don't be too discouraged if it doesn't last as long as you would ideally like :)