Nice job. For a first game, you did well. Plus it stars a seagull, so what's not to like?
As for a little feedback:
- If you added something that made it more visually clear which quests you have and haven't completed their quest for yet (like a glow around the character or object) that would help make things more clear.
- I think you played well into your art style, resulting in a bit of personality from the visuals.
- more of a minor nick pick, but if you had your character sprite swap to a swimming animation when on top of water, that would sell the idea of the seagull traveling across it better than just literally walking on water. You might even be able to have gotten away with just sinking the seagull's feet a bit more in the water to sell the illusion of it swimming without changing sprites.
- Another nick pick: I think you could have gotten away with adding some dialogue to the mermaid before giving you the seashell.