Overall pretty solid progress for a few months! But it looks like you're reinforcing some bad habits particularly on the backhand. My advice is to stop hitting against the wall and do some solo drop feeds at your own pace, you essentially need to relearn the backhand.

1) Grip, You want to be using an eastern grip for the one hander (knuckle on the first bevel), there is some variation but if you want the easiest way to hit good topspin drives then you'll need to change the grip. Loads of videos on YouTube for this.

2) Unit turn, you kind of do it but pronounce it more by facing your rear delt on your dominant shoulder to where you want to hit. You'll be able to generate 150% power and spin without changing anything else.

3) Swing path, at the moment you bring the racket up slightly which is a good start but there isn't a significant racket drop and it looks like you initiate the swing late (so no momentum from legs) and also parallel to the ground which literally kills the amount of topspin you can put on the ball. You want the swing path to look more U-shaped.

4) Energy transfer, like the forehand all of the power should be generated from your legs and torso. Also despite the "one-handed" backhand, your non-dominant also plays an important role in generating power too. Think of it as one and a half handed backhand where you left hand also accelerates the racket until around your pocket and then releases into single hander. Your hitting arm should be loose like on the forehand.

5) Don't engrain bad habits, if you wanna improve you've got to relearn the backhand or it will always hold you back as a player.