Hey not bad for your first one!
You should really add to this
add some music
more enimies, different ones too, not just the arrow, maybe like an arrow that moves back and forth on the platform if you can do it
maybe more levels?
Character select (I know thats pushing it lol)
definetly sounds though and a finish screen where you know "You Win"
I know you said you dont know how to do more levels but maybe you could use a next frame button or a next scene button to go to the next level if you collect enough circles
I hope this doesnt get blammed but it might
but it be a good game if you added more things :) good work and good luck