Let's compare:
apt update
Get:1 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Hit:2 http://archive.ubuntu.com/ubuntu bionic InRelease
Hit:3 http://ppa.launchpad.net/certbot/certbot/ubuntu bionic InRelease
Get:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]
Get:5 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Get:6 http://archive.ubuntu.com/ubuntu bionic-updates/main Sources [517 kB]
Get:7 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages [2,237 kB]
Get:8 http://archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages [1,749 kB]
Fetched 4,755 kB in 5s (875 kB/s)
Reading package lists... Done
Building dependency tree
Reading state information... Done
All packages are up to date.
apt-get update
Get:1 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]
Hit:2 http://archive.ubuntu.com/ubuntu bionic InRelease
Hit:3 http://ppa.launchpad.net/certbot/certbot/ubuntu bionic InRelease
Hit:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease
Get:5 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]
Fetched 163 kB in 1s (112 kB/s)
Reading package lists... Done