My two-cents:

Definitely wear proper footwear...barefoot would be better than sandals.

You have good handspeed, so why swing for a homerun on every punch? Short quick punches are just as effective. Jab, work the jab to set up the other shots.

As mentioned, get your guard up, throw the punches from the guard, return just as fast.

You have youth on your side, work on fundamentals, and get a good coach to make sure you don't develop bad habits.

Also, when the bag is swinging around, don't wait for it to stop, or stop it...It's your opponent, always in motion, move with, and away from it. Jab in, jab out, keep your distance. You'll go far lil' man! Good stuff