Welcome Klara. We all start where we start and there is no shame in that because you are beginning a journey. The collar is perfectly functional, so for that alone, it's a success. The fact that Rita likes it is a bonus. You have figured out how to make it with the tools you had on hand. The next step is learning how to make it match the image in your head.
Leather working, like most other things, is a mastery of a bunch of little things that allows you to create what you envision. Like learning how to sharpen your tools, learning the best way for you to hold/control a tool or learning the order of steps for a project.
You've made a fine start. I hope you decide to continue.