This looks really good for a first project!
I’m quite new to knitting too, and I find I often (especially when I first started!) either add stitches or lose stitches. I found a good way to learn where I was going wrong was to know exactly how many stitches I had on my needles at all times. So, say you had 20, you could count as you went, which would take a while, but then you know if you had 21/19, that you’ve done something wrong with that last stitch you made, and then you can learn how to reverse your mistakes.
It’s all a learning process, but the main thing is you’re enjoying it!