Alright so as this is your first game I would just like to tell you don't take this feedback too harsh these are just mistakes that we all make when we start. Speaking of starting where do we start...
- Textures: Probably here, so it's not hard to notice you are using unity so few pointers, when you click on a imported texture you'll find options where you can find compression and filtering. Both of these are the bane of pixelart, first filtering is responisble for the blurry edges around sprites, for pixelart you should turn it off, compression is the thing that combines close colors together leading to some artefacting on pixelart. Also try not to mix pixelart and traditional digital art as it's hard to mix them together and make it look good.
- Combat: As I see a lot of people already have touched upon it... it's not the best, generaly a good combat allows for both player expersion and strategy, making melee combat ain't easy ( checked that out this jam ) for it you usally want the combat to revolve more around distance, timing and croud control, meaning restricting the speed the player can attack, making attacks have a distance ( you have that ), and making the enemies follow simullar rules so that when a player is surrounded he'll need to think on his feet and deal with combat on many fronts, but... there is no one recepe game design is all about the needs of the game and making good combat is complex, so those are only pointers of what I would do, but I also have a lot more years behind me to back up those systems in code.
- Small Things: The bar at the top is wierd as it never resets between levels, it would be probably a better decision to just make it depleate faster but reset between levels. UI is scaling the whole background sprite, you should generaly do 9 sliced textures meaning that you set it in engine to keep corners scale edges in one direction and middle in both so there is no wierd streaching. Sound design the game lacks sfx for enemy attacks and getting hit both important informations to translate to player. Visual cues or lack there of I can't really tell if enemies actuall attack me or not it's honestly hard to judge if I'll get hit so health becomes less something to keep and more like a counter of how many enemies I delt with.
But hey it's still a solid entry and I wouldn't want you to discourage you even slightly. Making a game in a week is overwhelming and getting it done is a success in it of itself kudos.