Warning about updates after installing Kali linux tools
The LionSec Katoolin GitHub webpage clearly warns Katoolin users to be careful when updating software.
Before updating your system, please remove all Kali-linux repositories to avoid any kind of problem.

All kinds of problems can occur if you don't do this.
The Katoolin script is the cause of some of your problems. You don't need the repositories that the Katoolin script added anymore, so restore your sources.list file in /etc/apt/sources.list
back to the default for a fresh installation of Ubuntu 18.04.
Make a backup copy of sources.list.
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
Open /etc/apt/sources.list
for editing in nano text editor:
sudo nano /etc/apt/sources.list
Replace the entire contents of your existing sources.list with the following default 18.04 sources.list:
deb http://archive.ubuntu.com/ubuntu/ bionic main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ bionic-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu bionic-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu bionic partner
Press the keyboard combination Ctrl+O and after that press Enter to save the file being edited. Press the keyboard combination Ctrl+X to exit nano.
Run this command after changing sources.list to refresh the list of available software. This is the most important step, so please don't skip it.
sudo apt update
After running the above commands the package management in your Ubuntu 18.04 should go back to normal.
Spotify
You got the following error message:
Gtk-Message: Failed to load module "gail" Gtk-Message:
Failed to load module "atk-bridge" (spotify:15787):
Gtk-WARNING: cannot open display: :0
It looks like the Spotify snap package might work again after switching the channels. Run the following command to switch the spotify snap package's channel:
sudo snap switch spotify --edge
sudo snap install spotify
– karel Jul 31 '19 at 03:50