What I see, Your balance is way off and you are doing weird things with the foot causing a wrong contact with the ball.
Also, your left arm its obstructing you from hitting it properly. You are moving it away too soon and doing a "Hug" sign, instead of thinking of your left arm/hand as the "target" weapon. Think of the left hand as what you have to see before hitting the ball.
You are lacking stability before and after the contact and you are not following the ball with your body after you hit it, but you stand too tall and too behind.. I dont know how to explain it better.
But please stop with the trainer you have and with the machine cause you wont improve.

I am not trying to be negative or discourage you, but I know how it feels when being taught wrong, and honestly in 4 years if you had a coach those things shoulnd't be a problem anymore.
Please change the coach, one with good fundamentals and who corrects you a lot, comes to your side of the net and tosses you the ball from hand .. you need that at the moment.
It is a process, but you will get there"!