Glide slope is a part of Instrument landing system (ILS) That guides you vertically on to the runway, touch down point at a steady 3° slope( on most cases, can be higher than 3° in some airport) That is glide slope. The computer makes a sounds whenever you deviate from the glide path of 3°. That is either you are too high or too low. Try and capture back the glide slope. If you are too high descent a bit more. If you are too low slow down your rate of descent.( In some cases you might have to even level off). The glide slope indicator just to the left of your altitude indicator in HUD is a good reference. You can also choose to follow papi lights just to the left of the runway touch down point.
And also I believe you fly low on glide slope. Because as you mentioned the sound goes off when you increase the speed. Its actually not the speed but you halt your rate of descent as a reaction of increasing the speed. That makes you capture back the glide spope and the alarm goes off.