GUI 1.16.5

[Hyrancood]

Hello! I'm beginner in minecraft modding.

I want to create a GUI, that opens then key pressed, with buttons. I already create and register a key, but I faced with some troubles when try to make a interface.

Firstly, if I want add items to the player inventory when the button is pressed, should I create container? And how to make the interface open when key pressed?