Hi Agrim, for a first game made in such little time this is awesome! Being so early into your game making career and working as a solo developer on a 3 day game jam is crazy but considering that you've done well.
There are some obvious things I'm sure you'll improve on over time, mainly some of the collision being a bit off and a death box off the bottom of the screen would be a great addition. One more suggestion I'd make for a 2D platformer like this is the addition of "coyote time", if you're not aware of what this is then you can learn easily online. It is essentially a mechanic added to jumping functionality that gives lenience to the player when jumping between platforms. If they've just fallen off a platform and press the jump input a little too late we still apply the jump, it makes the player feel more in control and is something that is definitely worth learning about especially as a new developer!
Awesome work, keep learning and growing, I hope to see "second game" soon!