I am new with RaspBerry PI 4 and have many questions, could you please help me with this?

I installed Ubuntu 20.04 on this RaspBerry but when I try to download a program, like Google Chrome or whatever program I think about and try to install it, it says that the architecture (amd64) is not the one that I can run (arm64). I do not really know what this means.

Arm64 is generally the type of processor used in phones, and tablets and other small devices. Amd64 is the one generally desktop/laptops use. Raspberry Pi is a special breed.

is there a website that I can get codes from

Inputs for some buttons

To turn on some lights and to power on and off a raspberry pi