One thing many fail to learn is that to go down sometimes you need to pull up. As you increase your angle of attack you reach a point where the increase in drag far surpasses the increase in lift. Learn how slow you can get it and still have decent control and you will find if you maintain that speed with the power off it will descend steeper at a slower forward speed. One thing to note is if you are descending too fast just increase the throttle a little and it will stretch the glide, do not pull up more as you will likely stall or at least land even shorter.