I see that you are running wrong commands in the command line and that's why you are getting error messages. The guide says that you need to change directories but you are simply trying to run the path you need to move to instead of "telling" the command line you want to move to that other directory (the
cd command does that).
If you don't know how to work with the Linux command line, we suggest you read some online tutorials so you know how to work with the command line. If you require further help to work with the command line, we suggest you look for someone who can help you with that, we do not provide professional services. We can guide you to do different actions in the stack but we can't help you with every little step you need to perform to configure something.
As I mentioned above, I think you didn't configure WordPress properly and that guide should help you to finish with the configuration. Let us know if you still find issues when accessing the site after finishing with the guide.