Hey sky.
Its probably quite a long answer for that question if I was to explain all the needed code but I can give a quick explanation on how i have made enemies and items.

If you would like to see a working example of items the witch hunt game gde project is downloadable from the sonus game library.

Basically I had a variable for each item. Such as potions. And when the player object collided with a obtainable potion object, the potion object would play a little audio, increase the potion variable count and then destroy itself.

As for enemies coming  towards a player. I set 2 global variables to keep track of the players X and Z coordinates. Every time the player moves these variables get updated.

Then in an enemy periodical event they check If they are higher or lower than the player coordinates and adjust their own by 1. Then you can adjust how fast you want the enemy to move by adjusting the delay property on the object.

It's probably not a simple answer but I do plan on making a tutorial about It. Both of these will be included in the fighting game tutorial series.

Hope this helped a bit.

I had both these same exact questions. I am looking to make a fighting game of sorts in the gde, and i don't know how to go about making maps, and i now know about how to make enemies, thanks for that.