Having issues installing and running gitlab on clean server

Hi,

I tried to install gitlab on an ubuntu server 18.04.4. There is currently only a jenkins and apache2 running, nothing else. I followed this guide: https://about.gitlab.com/install/#ubuntu

During the installation everything was 'green' until this message appeared in red: Error executing action 'restart' on resource 'service[alertmanager]'

Mixlib::ShellOut::ShellCommandFailed ------------------------------------ Expected process to exit with [0], but received '1' ---- Begin output of /opt/gitlab/embedded/bin/chpst -u root:root /opt/gitlab/embedded/bin/sv restart /opt/gitlab/service/alertmanager ---- STDOUT: timeout: down: /opt/gitlab/service/alertmanager: 0s, normally up, want up STDERR: ---- End output of /opt/gitlab/embedded/bin/chpst -u root:root /opt/gitlab/embedded/bin/sv restart /opt/gitlab/service/alertmanager ---- Ran /opt/gitlab/embedded/bin/chpst -u root:root /opt/gitlab/embedded/bin/sv restart /opt/gitlab/service/alertmanager returned 1

Final message at the end is the following:

Running handlers:
There was an error running gitlab-ctl reconfigure:

service[alertmanager] (dynamically defined) had an error: Mixlib::ShellOut::ShellCommandFailed: Expected process to exit with [0], but received '1'
---- Begin output of /opt/gitlab/embedded/bin/chpst -u root:root /opt/gitlab/embedded/bin/sv restart /opt/gitlab/service/alertmanager ----
STDOUT: timeout: down: /opt/gitlab/service/alertmanager: 0s, normally up, want up
STDERR:
---- End output of /opt/gitlab/embedded/bin/chpst -u root:root /opt/gitlab/embedded/bin/sv restart /opt/gitlab/service/alertmanager ----
Ran /opt/gitlab/embedded/bin/chpst -u root:root /opt/gitlab/embedded/bin/sv restart /opt/gitlab/service/alertmanager returned 1

Running handlers complete
Chef Client failed. 604 resources updated in 04 minutes 10 seconds
dpkg: Fehler beim Bearbeiten des Paketes gitlab-ee (--configure):
 Unterprozess installiertes gitlab-ee-Skript des Paketes post-installation gab den Fehler-Ausgangsstatus 1 zurück
Fehler traten auf beim Bearbeiten von:
 gitlab-ee
E: Sub-process /usr/bin/dpkg returned an error code (1)

I am not experienced in managing a server, so it might be some basic stuff i forgot. Can someone please help me?