Deleting a directory

I am working through a tutorial - The Linux Command Line for Beginners - and I want to delete my work so far and start over. I have a directory called tmp within the root directory which has a solid green box around it. If I ls this directory I get a config error. I don't know what this means and I can't delete it. Can you help please?

peter@peter-HP-ProDesk-400-G5-MT:~$ cd /
peter@peter-HP-ProDesk-400-G5-MT:/$ ls
bin    dev   lib    libx32      mnt   root  srv       timeshift  var
boot   etc   lib32  lost+found  opt   run   swapfile  tmp
cdrom  home  lib64  media       proc  sbin  sys       usr
peter@peter-HP-ProDesk-400-G5-MT:/$ cd tmp
peter@peter-HP-ProDesk-400-G5-MT:/tmp$ ls
config-err-MUm7iD
mintUpdate
MozillaUpdateLock-4F96D1932A9F858E
systemd-private-bc10ea19133a48fd8e526c45b179e6cf-colord.service-CPuYYO
systemd-private-bc10ea19133a48fd8e526c45b179e6cf-ModemManager.service-dUDoww
systemd-private-bc10ea19133a48fd8e526c45b179e6cf-switcheroo-control.service-Z8zyOX
systemd-private-bc10ea19133a48fd8e526c45b179e6cf-systemd-logind.service-7z9IHP
systemd-private-bc10ea19133a48fd8e526c45b179e6cf-systemd-resolved.service-vLAsUl
systemd-private-bc10ea19133a48fd8e526c45b179e6cf-upower.service-fxuTWM
tutorial

I have copied the screen as above but note: the directory entitled 'tmp' has a green solid box over it but is not shown on this screen grab. Also the word 'mintUpdate' shown in the output of running ls int he tmp/ directory has a solid green box not shown.