I'd appreciate if you'd give further instructions about how things work. You can also work on adding more frames to the sprites walking animation to make it appear more smoothly rather than choppy. I also don't seem to understand what I'm supposed to do in the boss fight. I really liked the smooth menu animation, but the game itself needs some foundations. The Music, seems to be recorded off a microphone so the quality is a bit bad, I'd recommend searching the music up on youtube and using a youtube to mp3 converter and import the mp3 file to scratch.
Though Newgrounds doesn't really allow the use of copyrighted music as far as I know (If I remember correctly, the title screen music seems to be a version of the Pursuit theme from the ace attorney series and the soundeffects are from Sonic Mania, the other I cannot identify).
It's not really the greatest thing out there, but as a scratcher to another scratcher my honest advice is to work more on it. Practice art and try making things seem more smoother when the player jumps or runs, work on the sprites and more appealing.
For art I'd suggest you look for inspirations and practice drawing by using reference until you get the understanding of things.
Hope this advice helps.