Installing GitLab on existing GIT setup

Hello everybody. This is my first post here.

A year ago Ive setup a GIT server on local machine (with Debian and Apache). User is git and group is git. Home folder is /home/git. I have there /gitprojects folder with laravel projects repos and /gitlaravelmodules with modules repos for Satis repositories. Everything worked well over last year. But now need some neat GUI to manage the project and see commits and everyday progress

I tried to install GitLab on this server on 8010 port but it fails at the moment when it tries to create git group and user. Ive already searched for clues in /etc/gitlab/gitlab.rb but everything is commented there and also tried to backup and erase /opt/gitlab/embedded/cookbooks/cache/cookbooks/package/resources/account.rb
file as it seems to be the cause of the problem but i found it recreates itself automatically.

So the question is: how to install GitLab on existing GIT setup (with existing git user, group, his home directory and repositories).

My mistake - the problem was that user git was logged in. I logged it out and then the rest went fine