the game is normal, but there are bugs

Not bad for a first project; actually quite all right. The controls are fine and fluent, there are no bugs I could find, and there are at least two kinds of enemies.
Although there's space for improvements.

– First, there's no victory screen. Just an end flag which leads nowhere. It doesn't take a lot of time to add a "You win!" screen but helps you a lot to feel you "completed" the game.
– The game is too short to truly enjoy it. You can complete it in under a minute.
– Perhaps it's just me, but the game resolution feels a bit small. I'd change it a bit, make it larger. Not to mention the resolution on Newgrounds (the black area around) was chosen too big.
– I know Kenney gives away free assets, but these platformer sprites are a little bit too recognizable to be usable as anything else than a temporary placeholder because too many people use them already. If you don't want/can't draw your own, check (for example) OpenGameArt, there's a lot of free stuff, too.
– The health mechanic is a bit confusing.
• Things which hurt you take away half a heart. But an empty heart still doesn't kill you (might be confusing).
• Getting hurt three times subtracts a life and restarts the level. That is okay.
• Losing all lives restarts the level and refills your lives, too. Since it does essentially the same thing as the previous bullet point and there is no game over, it means you have infinite lives. You could just as well have written ❤ × ∞.

Good luck with your future projects. :)

Not terrible a few things;

1: The character somewhat blends in into the background making it hard to see where he is.
2: Change the goal to a locked door instead of a duplicate start flag
3: The platforms are a bit small