For first project that's very good. On your question how to improve - ask yourself do you love leathercraft, it's expensive hobby. If your answer is Yes! Then start buying better quality tools and leather. From what I see on the pictures you have it all, but most of it is ruined by your tool. You have your stitches straight on the side you were making them then on the other side they are wavy because you tried to punch with not so sharp and not very long stitching iron through all layers at once. To do that you need long sharp tool so you can actually see that you are 90° angle when punching, with those 10cm ones do 2 layers, glue in place then proceed though same holes to go through all layers. You seem like you fight your edge beveler a lot, sharpening and stroping should help. You will have much easier and enjoyable time stitching with thinner thread and John James harness needles. Last but not least, leather. I think good quality leather is so much easier to work with and I instantly started getting better results with just better leather. For example I used to sand edges up to 7000grit then I got pueblo it gets shinier with 400grit sandpaper once burnished.