Install and run both OpenProject and Gitlab on Debian 10

I want to install both GitLab and OpenProject to run together on one Debian 10 Machine.

So, First installed OpenProject and configured it to run on openproject.example.com which runs on Apache. and works great in address: openproject.example.com

then installed gitlab-ee and configured it to run on gitlab.example.com which uses nginx.

opening gitlab.example.com show openproject.example.com.

restarted. and this time i get: Service Unavailable

The server is temporarily unable to service your request due to maintenance downtime or capacity problems. Please try again later.

How can i do this?

P.E: And Finally, how can i install and run jenkins on same machine, with jenkins.example.org?