I have a custom module in Drupal 8 called hello world. In that module, I make a custom block called Hello World. I try to enable blocking and set its region to "sidebar_second" from inside my module. I'm also trying to make it only visible in a certain type of content and change dynamically. The content of the block must be a link to the other nodes in that type of content. I can not figure out how to do that, can anyone show me how to do all that?