How to install screenlets on Ubuntu 18.04?

I want to install Screenlets and I tried the following bash:

#!/bin/bash
sudo dpkg -l python-wnck >/dev/null 2>&1
if [ $? == 0 ]; then
  echo "OK"
else
  echo "Install python-wnck"
  sudo apt -y install libwnck22
  wget -c http://archive.ubuntu.com/ubuntu/pool/universe/g/gnome-python-desktop/python-wnck_2.32.0+dfsg-4_amd64.deb
  sudo dpkg -i python-wnck_2.32.0+dfsg-4_amd64.deb
  sudo apt --fix-broken -y install
fi
sudo dpkg -l python-gnomekeyring >/dev/null 2>&1
if [ $? == 0 ]; then
  echo "OK"
else
  echo "Install python-gnomekeyring"
  wget -c http://archive.ubuntu.com/ubuntu/pool/universe/g/gnome-python-desktop/python-gnomekeyring_2.32.0+dfsg-4_amd64.deb
  sudo dpkg -i python-gnomekeyring_2.32.0+dfsg-4_amd64.deb
  sudo apt --fix-broken -y install
fi
sudo add-apt-repository -y ppa:screenlets/ppa
sudo sed -i 's/bionic/xenial/g' /etc/apt/sources.list.d/screenlets-ubuntu-ppa-bionic.list
sudo apt update && sudo apt -y install screenlets screenlets-pack-all

But all I get is this:

tobi@tobi-System-Product-Name:~$ #!/bin/bash
tobi@tobi-System-Product-Name:~$ sudo dpkg -l python-wnck >/dev/null 2>&1
tobi@tobi-System-Product-Name:~$ if [ $? == 0 ]; then
>   echo "OK"
> else
>   echo "Install python-wnck"
>   sudo apt -y install libwnck22
>   wget -c http://archive.ubuntu.com/ubuntu/pool/universe/g/gnome-python-desktop/python-wnck_2.32.0+dfsg-4_amd64.deb
>   sudo dpkg -i python-wnck_2.32.0+dfsg-4_amd64.deb
>   sudo apt --fix-broken -y install
> fi
OK
tobi@tobi-System-Product-Name:~$ sudo dpkg -l python-gnomekeyring >/dev/null 2>&1
tobi@tobi-System-Product-Name:~$ if [ $? == 0 ]; then
>   echo "OK"
> else
>   echo "Install python-gnomekeyring"
>   wget -c http://archive.ubuntu.com/ubuntu/pool/universe/g/gnome-python-desktop/python-gnomekeyring_2.32.0+dfsg-4_amd64.deb
>   sudo dpkg -i python-gnomekeyring_2.32.0+dfsg-4_amd64.deb
>   sudo apt --fix-broken -y install
> fi
OK
tobi@tobi-System-Product-Name:~$ sudo add-apt-repository -y ppa:screenlets/ppa
sudo: unable to execute /usr/bin/add-apt-repository: No such file or directory
tobi@tobi-System-Product-Name:~$ sudo sed -i 's/bionic/xenial/g' /etc/apt/sources.list.d/screenlets-ubuntu-ppa-bionic.list
sed: can't read /etc/apt/sources.list.d/screenlets-ubuntu-ppa-bionic.list: No such file or directory
tobi@tobi-System-Product-Name:~$ sudo apt update && sudo apt -y install screenlets screenlets-pack-all
Get:1 http://archive.getdeb.net/ubuntu xenial-getdeb InRelease
Err:1 http://archive.getdeb.net/ubuntu xenial-getdeb InRelease                                                                             
  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
Get:2 http://security.ubuntu.com/ubuntu xenial-security InRelease [107 kB]                                                                 
Ign:3 http://ppa.launchpad.net/inameiname/stable/ubuntu bionic InRelease                                                                   
Hit:4 http://ppa.launchpad.net/jonathonf/python-3.6/ubuntu bionic InRelease                                                                
Hit:5 http://us.archive.ubuntu.com/ubuntu xenial InRelease                                                                                 
Err:6 http://ppa.launchpad.net/inameiname/stable/ubuntu bionic Release                                                                     
  404  Not Found [IP: 91.189.95.83 80]
Get:7 http://us.archive.ubuntu.com/ubuntu xenial-updates InRelease [109 kB]                                                      
Hit:8 https://download.sublimetext.com apt/dev/ InRelease                                                            
Get:9 http://us.archive.ubuntu.com/ubuntu xenial-backports InRelease [107 kB]                                        
sh: 1: /usr/lib/cnf-update-db: not found                  
Reading package lists... Done
E: Failed to fetch http://archive.getdeb.net/ubuntu/dists/xenial-getdeb/InRelease  Clearsigned file isn't valid, got 'NOSPLIT' (does the network require authentication?)
E: The repository 'http://archive.getdeb.net/ubuntu xenial-getdeb InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: The repository 'http://ppa.launchpad.net/inameiname/stable/ubuntu bionic Release' does not have a Release file.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
E: Problem executing scripts APT::Update::Post-Invoke-Success 'if /usr/bin/test -w /var/lib/command-not-found/ -a -e /usr/lib/cnf-update-db; then /usr/lib/cnf-update-db > /dev/null; fi'
E: Sub-process returned an error code
tobi@tobi-System-Product-Name:~$ 

I think sudo apt-get update doesn't work for me, but I don't know how I can fix this.

output of apt-cache policy python3-software-properties:

python3-software-properties:
  Installed: 0.96.24.32.4
  Candidate: 0.96.24.32.4
  Version table:
 *** 0.96.24.32.4 100
        100 /var/lib/dpkg/status
     0.96.20.7 500
        500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main i386 Packages
     0.96.20 500
        500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
        500 http://us.archive.ubuntu.com/ubuntu xenial/main i386 Packages