1) I watched a few of your game serves (unfortunately it desyncs all the time after a while). I think overall it's alright : you're supposed to be under pressure on your 2nd serve, but manage to win a bit more than 50% of the points when facing an opponent of a similar level.
You can improve on 2 points, though :
- you should back right away after your serve, of about 50cm ; there you're often on your baseline or just 1 step behind, which isn't good when you get deep returns ; on the other hand, you'll have to be even more on your toes to reach the shorter returns, as you already struggle a bit to reach them
- use the service aiming preview to learn the timing required to aim closer to the lines ; many of your serves are way too near the center of the service zone
2) For your net coverage, you have to improve your footwork and positioning ; the CPU does that nearly perfectly, and you have a good margin for improvements in that zone (which helps you to be less annoying by the return of serve as well, as explained above).

ie: volleying is much less forgiving on mispositioning and being late on the ball than rallying from the baseline.