The language pack maintainer did not login anymore for quite a while. You can contact him/her via the messaging system of https://lang.moodle.org, but I assume the person has left the project.
The translation work is voluntary - people come and go. Are you interested in maintaining Sinhala?
Thanks for the offer. I doubt whether I am the right person. Although I have installed the Sinhala language pack out of curiosity, it is only since last Saturday I use it in a real course! I would edit my local version first and see how it goes.
My immediate problem is to find out the connection between a language strings and where it appears in Moodle. For translation I need to know the context.