Hey there, welcome! That's some nice work! May I analize it a bit? I'm no master of the art, but I can give you a couple of tips.
Let's start with what you did wrong:
The anatomy is all over the place, which is weird, your mermaid drawing has better proportions, try to learn from that. In the image it shows, I drew the image in the middle to show what I'm seeing when I see your pic, some weird pose. In the right, is my sketchy try at the pose, it's more balanced, but it looses the charm, you're gonna have to make the good one yourself haha. What's really grinding my gears, is the positioning of the eyes. It's all over the place. The heads in the middle show a quick way to fix that. You should study anatomy. But in the meantime, there's that.
Now, the good:
It's anime, sure, but you have your own style there, and I like it very much! The joints were misplaced but the proportions are awesome and unique, in a way, try to keep that style and make it better. I want to see where this goes!