For the enemies, here is a very simple AI:
If Enemy.X > Player.X : Enemy -> Simulate Control -> Left
If Enemy.X < Player.X : Enemy -> Simulate Control -> Right
Note that this doesn't include jumping, which if you need I can help with that, just let me know.
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For the Healthbars, try:
Enemy -> On created : Create Object -> Healthbar. Make sure that the position is Enemy.X, Enemy.Y-50 (Or change 50 to whatever is needed to position it properly), then Healthbar -> Pin to Object -> Enemy (Make sure those two actions are in the same event)
If you need any more help or want me to create a mock-up and share it with you then let me know.
I got the movement code working but I need help individualizing the X and Y, I used to use scratch where the variables were automatically individualized. Also how do you even make a health bar.