How to create a wave system and a random loot drop system?

I posted a discussion yesterday so I hope I’m not spamming. Does anyone know how to make enemies respawn on a round based system and make them have a random chance of dropping an item? And at the end of a wave a chest spawns dropping a random but guaranteed item.

use a spawn behavior for spawning the enemies. a random behavior connected to a emit behavior for the dropping of the item. i don’t understand the last one