ii
So the person who originally developed it is gone? No documentation?
Sounds like you took a job above you’re experience level, been guilty of that, had no idea what the code was doing or where to start.
If you know JavaScript for Unity you shouldn’t have too much trouble going over to C#. If you want a thread to help you do your job, this is not the place to do it. The Answers forum is where you can ask technical questions but no one is going to solve problems for you, gonna need to work that out.
If you really have no support for just starting it doesn’t sound like a very organised place to work or they assumed you were experienced enough to be fine.