How to receive messages from Pub-Sub google?

Question

Google

Hello.
Here I have a problem, I can not figure out how to receive messages from PubSub from the google server.
I need to receive a message every 3 hours, for this I also somehow need to use the Scheduler from google.
I read the documentation, but it is written there quite unclearly, to whom the link is interesting .
I ask a question so that they explain to me in words what is there and how, so that I can ask the question and understand everything.
Thank you!

Answer 1

start by copy-pasting the code