This a guide I have written during my installation of openvas.
All commands are taken from internet, and maybe something could be useless, but for me it worked 
Please try it and give me feedback to improve and fix the guide
Hope it helps
sudo apt update; sudo apt -y dist-upgrade; sudo apt -y autoremove
sudo apt install -y postgresql
sudo systemctl status postgresql
sudo -u postgres createuser root
sudo -u postgres createdb -O root tasks
sudo -u postgres psql tasks
create role dba with superuser noinherit;
grant dba to root;
create extension "uuid-ossp";
update pg_database set datallowconn = ‘true’ where datname = ‘tasks’;
\q
sudo apt install -y postgresql-contrib postgresql-server-dev-10
cd /usr/local/src
sudo mkdir -p openvas/debs
cd openvas
sudo add-apt-repository -s ppa:mrazavi/openvas
sudo apt update
sudo apt install -y dpkg-dev debhelper cmake pkg-config libglib2.0-dev libgnutls28-dev libgcrypt11-dev libsqlite3-dev libgpgme11-dev rats libopenvas9-dev smbclient
sudo su -
apt source openvas9-manager
cd openvas9-manager-7.0.3 ← check your version
dpkg-checkbuilddeps
vim debian/rules
override_dh_auto_configure:
dh_auto_configure -- -DLOCALSTATEDIR=/var -DSYSCONFDIR=/etc -DBACKEND=POSTGRESQL
echo "usr/lib/openvasmd/pg" >> debian/openvas-manager.dirs
echo "usr/lib/openvasmd/pg" >> debian/openvas-manager.install
dpkg-buildpackage -uc -us
mv …/*.deb …/debs/
apt-mark hold openvas9-manager
apt install -y openvas9
CHECK that Openvas-scanner is active
dpkg -i …/debs/openvas9-manager*.deb
openvasmd --user=admin --new-password=XXXXXXXX
openvas-manage-certs –a –f
sudo apt-get install texlive-latex-extra
vim /etc/default/openvas-gsa
# To allow <host> as hostname/address part of a Host header:
ALLOW_HEADER_HOST="XX.XX.XX.XX"
# To set listening address:
LISTEN_ADDRESS="XX.XX.XX.XX" <–Openvas IP
PORT = 9390
sudo service openvas-gsa restart
reference: Install OpenVas9 with Postgresql in Ubuntu 16.04LTS · sadsloth.net