Correcting faulty sidespin

I started learning TT almost 12 years ago. I learned it by looking others playing and nobody guided me. One year ago I participated in a tournament and came to know that difference of the levels of my playing and others who are defeating us. As I asked the winners, I came to know that they took extensive coaching and hence came to know about PingSkills on surfing YouTube TT tutorial channels.

Your videos help me correct actions and build the techniques a lot; and I am improving slowly. One action I failed to correct, and I need your help. Due to faulty style of play for so many years I prone to make "hook" while taking forehand top spin shot; i.e., my wrist does not remain straight; and therefore while taking forehand top spins shots, I am always delivered with side spin or side-top spin. This makes me very difficult to deliver a good shot while countering a heavy backspin.

As I do not have a good partner who can indicate my faults, it is becoming extremely hard to correct my faults. Due to this I sometimes do shadow-practice in front of mirror; but it is not much effective. Please guide me how to correct my action.