How to learn ROS2 properly

edit

Hi,

Sorry it is a bit bad topic. My problem is ROS2 is too complicated and hard to track.

there is lots of term and there is no proper description of them.

For example I want to publish lidar data, there is a laserscan msg type, it says some parameters. But there is no example how can i made it correct. how should i publish tf2 data? with same node or different. is there anything that I should do?

How people use ROS2 and do this work?

In short I cant image workflow in ROS2 and I want to understand ROS's logic.

ROS2 is like more complicated video edit program, and i need to learn its language? any advise?

thanks,