Before anything, i want it clear that i want you to improve, not quit, and that my criticism is not meant to offend anyone. PS: The list is from least important to most important:
First off, the lighting in the first level gets duplicated whenever you die, in the screenshot below, i died 7 or so times, and as you can see, i cannot see a thing because of the duplicated lighting
Secondly, in the second level, there are holes in the ground that when you fall through, the level does not reset. That wouldn't be a problem if the "R" key restarted the level you're on, but you did not implement that, so the only thing you can do is close the game, and reopen it, starting you at level 1
Thirdly, in the first level, there is a chance that the box that teleports you to the second level won't work, and you'd just collide with it and nothing would happen.
Fourthly, if you press the up arrow with the left arrow, you double the speed of the player, allowing you to jump way further than you should, making some levels insultingly easier than usual.