Your game looks good visually and gameplay is fun too. Eventhough you used premade assets, i think you did a good job blending them and your level design is pretty good as well. You managed to capture the Castlevania feeling very well. The flaws of your game are;
-You cannot damage enemies with melee attack. This is a serious problem since your arrows are limited. Also there's no need to hold d button to execute the melee attack.
-There's sprite tearing in your tilemap. I don't know how to fix that in Godot but it can be fixed with simple sprite atlas in Unity, probably it could be fixed in Godot with the same way.
-You cannot kill the boss if you're out of arrows since it's the only way you can damage it. When you jump to the platform in the boss room, boss cannot follow you there and stuck on the edge of the platform. I would give that water mage boss some kind of range attack as well. Also you need to add a healthbar to the boss. Currently the boss fight is quite broken.
Overall i really enjoyed the game, it really scrathed my Castlevania itch! :) I hope you turn this into a full game. Good job and good luck