I set up a GitLab self-hosted instance and its working fine, my problem right now is that I don't really understand how the frontend works. Mostly because I've been focusing on the backend and because I couldn't find documentation about it either. I wish to understand how I can comment out things I don't want to show for the user or in the overall design, change aspects and text, and overall have control of the frontend.
I'm running on Debian 9, the setup was made with Bitnami using Google VM. As far as I understand I have to manually change the files I want, but I really don't understand the structure of this type of frontend.
What language do I need to know here and where should I find the documentation, how to find the correct directory and files, etc.?