#  First update the apt repo list:
$  sudo apt update

#  You can improve Fonts via gnome-tweaks, it's the easy way....
$  sudo apt install gnome-tweaks fonts-noto fonts-hack-ttf

#  Now launch Tweaks, then go to Fonts: Hinting -> Full and Antialiasing -> Subpixel (For LCD Screens).
#  To do if not stunned, Open Tweaks - again go to Fonts, then Change your Default Fonts as:
#  Change Document Text to: Noto Sans Regular 11 & Monospace Text to: Hack regular 13.

#  Gnome Desktop: Put the Dock at Bottom and make it shrink...        
$  gsettings set org.gnome.shell.extensions.dash-to-dock extend-height false
$  gsettings set org.gnome.shell.extensions.dash-to-dock dock-position BOTTOM
$  gsettings set org.gnome.shell.extensions.dash-to-dock show-mounts false
$  gsettings set org.gnome.shell.extensions.dash-to-dock click-action 'minimize-or-overview'

#  Gnome Desktop: Autohide Top bar, note after install requires a reboot for Gnome Tweaks to see it...
$  sudo apt install gnome-shell-extension-autohidetopbar

If you want to undo that:
gsettings reset org.gnome.shell.extensions.dash-to-dock click-action

#  Install Media Codecs
$  sudo apt install ubuntu-restricted-extras

#  Install Extra Archive Utilities
$  sudo apt install rar unrar p7zip-full p7zip-rar

#  You can install Ubuntu Cleaner by running the following commands:
$  sudo add-apt-repository ppa:gerardpuig/ppa
$  sudo apt-get update
$  sudo apt-get install ubuntu-cleaner

#  Add a GUI Firewall:
$  sudo apt-get install gufw

#  Remove Crash Reporting:
$  sudo apt remove apport apport-gtk

#  Install Timeshift System Backups:
$  sudo add-apt-repository –y ppa:teejee2008/ppa
$  sudo apt-get update
$  sudo apt-get install timeshift

* FYI - mostly, you add a PPA using add-apt. We’ll use same add-apt to remove a PPA. Use the following command in terminal:
sudo add-apt-repository --remove ppa:PPA_Name/ppa

Install and Setup FireJail to secure web browser...