Hey Jaspert, you look good. I'm also in Melbourne and just bought a ball machine today to practice, having picked up the game about a year ago at 37. Whereabouts do you play?
With regards to the topspin serve, I'm no expert but you can probably afford to have your contact point a little bit higher and the ball toss a little bit more inside the baseline, though hard to tell from this angle. You probably don't even need to use a pure top spin serve, can get away with some combination of top spin and slice (the kick serve), which allows for more angular momentum into the ball and will be trickier to return.