Can't Get CiviCRM BuildKit files From Repository
At that point in the install script, it is attempting to run sudo apt-get -y install for a bunch of packages.

It looks like you have added a ppa for midori but that does not have a bionic release yet.  You can run sudo add-apt-repository -r -u ppa:midori/ppa or find the entry for midori in /etc/apt/sources.list or /etc/apt/sources.list.d and comment it out and run sudo apt update

Once you can get sudo apt-get -y install to run cleanly on some (any) package, try again with the get-buildkit.sh script.

Note also that bionic comes with php 7.2 which is marked as 'not yet tested' in https://docs.civicrm.org/sysadmin/en/latest/requirements/#php-version so unless you are only interested in the very latest releases and debugging 7.2 issues, you probably want php 7.1 (see eg https://tecadmin.net/install-php-7-on-ubuntu/).  However, if you do that you'll need to install the 7.1 version of the php extensions.  Look at the php7.1-* list in the 'do_system_artful' function of get-buildkit.sh