Forget the mirror. If you are looking in the mirror, you can not have a hard focus on the front sight.
Here is some of what we teach.
Take a 3x5 index card, and mark an X on it.
Put the card on a wall that can withstand a bullet hit
Simply bring the gun up, get the sight picture and slowly press the trigger.
When the hammer or striker falls note where the front sight relative to the X.
That is where the bullet would have hit
Repeat as necessary until you get 10 in a row where the frontsight did not move from the X
Do this for no more than 15 or 20 minutes a day.
Okay 10 is your record. Tomorrow, try to break the record.
If your gun will allow you to balance a penny on the front sight, do it.
Bring to gun to your line of sight and break the shot without the penny falling off and without the front sight coming off the X. Once you get good at the penny start using a bigger coin and repeat as before