Showing health bar picture above event

Hello! I am new to this forum (and RPG Maker MV itself), so sorry if this has already been answered.

I was messing around in RMMV trying to create a pseudo-hack-n-slash style game, meaning no battle screens, just the map.

So, I made a slime enemy, and tried to show a health bar image above it.

Storing X and Y values of the slime, and showing/moving the picture on those values. (Also, switching to the next event page)

And the attack.

The "attack" event, removing health bar image and erasing the slime.

But when I test the game, the health bar image won't show up. (Health bar image is 100x100, if it helps. I haven't installed any plugins, too.)

This isn't gonna be a full project or anything, but I would like to figure it out for this test game, and any future projects.
Any help would be appreciated!

Map X and Map Y are the tile coordinates on the map itself.
You'll need Screen X and Screen Y to get the pixel coordinates on the screen position instead.

However, there are more problems with this event than just that, because you swith to the second page the screen position will not update when the event moves to a different position.