There is already support for translations in Gain Factory Reloaded. There is a topic on the community page about this feature, and it has a guide on how to install .lang files into the game. There is already a translation to ukrainian made by Misha279_UA under that topic. If you want to make a translation, you can rename and edit the existing en.lang file, and the changes will show up in the game.
Translations topic: https://itch.io/t/3839399/translations