congratulations for finishing your first jam!!!
i would say some things so you can improve your next game :
* the explosion and enemies animation are well done
* the UI is not, i mean, it's functional but it doesn't look good, my advice is this:
choose ONLY ONE typography for all the menu, and design your color palette for the menu, not based on the color of your level, but instead based on the feeling/theme/atmosphere that you try to communicate with your game. and choose a typography that reinforces that theme. same wiht the buttons, and the rest of the menu elements.
* i can't pass the second enemy because its always on the lava, so , my advice with this is check your enemy AI behavior, or make sure that they spawn/ roam between an area determined by 2 Vector2 variables, that way you ensure that your enemies will stay where you want them to.
* the healt bars : if you are going to use a slider as a health bar, remove the ball thingy that comes with the gameObject, otherwise, you could use a panel, and change it's fill value variable via code. (check internet for tutorials) is a much better way to do health bars, and also supports images , so you can add custom health bars designed by you.
*the player jumps way too high and move sideways like sliding, try to improve that by using a rigidbody to move the character, (using transform.translate or transform.positon will clip your character if he moves fast enough).
again congrats for making it to the end , and keep coding!!!