Advanced Gitlab and Redmine integration (integrating issues)

I have a Gitlab CE group consisting of multiple repositories. I want to use Scrum and Agile, so I have decided to use Redmine not only as an external issue tracker, but also as a scrum board for these issues. I prefer not to use the paid versions of Gitlab for scrum/agile capabilities, so I’m using a Bitnami Redmine+Agile VM. However, I want to keep my Gitlab issue tracker alongside Redmine so that I can have other people focusing on their low-level tasks and keep track of their own personal backlog.

I have gone to the Redmine configuration page on Gitlab to set up “Redmine integration”, but all it does is put a link that directs me to my Redmine project web page. I have the agile/scrum board and all the tools I need on Redmine already and I can set up my repositories just fine.

I can’t figure out how to have the issues integrate from Gitlab to Redmine so that when I update/create/close an issue on Gitlab, it will be similarly affected in Redmine (and vise versa, if possible). Is there something I’m missing, or is this level of integration just not possible?