Hi, and thank you for your interest!
Volume Control is being translated using Weblate, a web tool designed to ease translating for both developers and translators.
Translation project for Volume Control into Sinhala currently contains 65 strings for translation and is 3.0% complete.
If you would like to contribute to translation of Volume Control, you need to register on this server.
Once you have activated your account just proceed to the translation section.