How to make something like that?

How can I make GUI boxes showing when player do something action. For example: get item into inventory.
Something like that:

with the unity ui system. set a panel in one corner give it a vertical layout group-component.

add a child and style it like one of your notifications. save it as prefab.

if the player does some stuff, instantiate a object from that prefab to the panel. it will position itself automatically if you set up the layout group correctly