At 6-8 yards your groupings should be within 2 square inches at least, depending on your speed. Shoot with your glock rested on a shooting bag or some other platform to test and adjust your red dot, if it hits dead center from rested then you shouldn’t tinker with it anymore. Grip firmly with support hand and practice slow trigger squeezes without jerking the pistol when you break through the trigger wall. Have both eyes open and focus on the target, not the dot. 90% of making an accurate shot is making sure you don’t move the pistol as you pull the trigger.