Confused...

https://reddit.com/link/1i6hd3l/video/c29vslcz7cee1/player

I (19M) have been playing table tennis for 2 and a half years on and off. First half year with an old premade which played like a better hard bat and the next 2 with a DHS Premade with H3N on both sides. Played mostly with my brother without any coaching or proper club anywhere near me. Did drills and mutual practice for 3-4 months during this time. This is me against a random person in trials for national and the first time I watched a recording of myself playing. I'm the one on the farther side with the purplish shirt. I knew that I wasn't that good but what confused me the most is that I was not playing how I thought I was, if that makes sense. My major concern is my stance. I know I have to stay low and that is what I was doing in my mind until I saw myself in the video. How do I do what I am thinking or want myself to do? What would you recommend me to work on based on this video? I am pretty confident in my backhand in practice but even that didn't look as polished in this.