You are incorrect here. A Glock has THREE safeties.

1. Trigger Safety. To fire the pistol, the trigger safety AND the trigger itself must be deliberately depressed at the same time. If the trigger safety is not depressed, the trigger will not move rearwards and allow the pistol to fire.
2. Firing Pin Safety. the firing pin safety mechanically blocks the firing pin from moving forward. As the trigger is pulled rearward, the trigger bar pushes the firing pin safety up and frees the firing pin channel.
3. Drop Safety. The trigger bar engages the rear portion of the firing pin and prevents the firing pin from moving forward. As the trigger is pulled rearward the trigger bar lowers down the safety ramp and allows the release of the firing pin.

After firing, as the trigger is released, all safeties automatically reengage.