https://pimylifeup.com/raspberry-pi-ssl-lets-encrypt

I'm trying to follow this guide, but I'm stuck on the third step here (just the first command and its output):

$ gpg --keyserver pgpkeys.mit.edu --recv-key  8B48AD6246925553
gpg: failed to start the dirmngr '/usr/bin/dirmngr': No such file or directory
gpg: connecting dirmngr at '/run/user/1001/gnupg/S.dirmngr' failed: No such file or directory
gpg: keyserver receive failed: No dirmngr

The other three commands do not work either. Plus, when I do an sudo apt update, it gives me this output:

Err:1 http://raspbian.raspberrypi.org/raspbian stretch InRelease                                                  
  Temporary failure resolving 'raspbian.raspberrypi.org'
Err:2 http://ftp.debian.org/debian jessie-backports InRelease                                                     
  Temporary failure resolving 'ftp.debian.org'
Err:3 http://archive.raspberrypi.org/debian stretch InRelease                                                     
  Temporary failure resolving 'archive.raspberrypi.org'
Reading package lists... Done                                                                                     
Building dependency tree       
Reading state information... Done
All packages are up to date.
W: Failed to fetch http://raspbian.raspberrypi.org/raspbian/dists/stretch/InRelease  Temporary failure resolving 'raspbian.raspberrypi.org'
W: Failed to fetch http://ftp.debian.org/debian/dists/jessie-backports/InRelease  Temporary failure resolving 'ftp.debian.org'
W: Failed to fetch http://archive.raspberrypi.org/debian/dists/stretch/InRelease  Temporary failure resolving 'archive.raspberrypi.org'
W: Some index files failed to download. They have been ignored, or old ones used instead.

I don't think archive.raspberrypi.org is even used anymore, right? Well, either way, I couldn't search up a search including on Stackoverflow.

Any help would be appreciated.