Gitlab Installation Ubuntu 18 VPS


I am new to Gitlab and trying to install Gitlab CE on a Strato VPS.
So I am currenty following this tutorial:
As to Step 7, gitlab seems not to be able to start all services. Sometimes, prometheus could not be started, sometimes unicorn etc… The crashed services seem to be random.
This results in constant error 502 or 500.

Most of the time, it seems that prometheus or redis is crashing.

How may I find the source of the error(s) and what information are needed?
Thank you in advance.

EDIT: After a server Restart, Prometheus and Alertmanager are always down.

Nevermind, switched to Docker image.

I’d like to recommend following the official guide as sometimes the guides from external sites are outdated.

This guide results in the same behaviour.