Hi there. I've read your descriptive and understand that you are facing problems with your existing mobile app which crashes the camera and forces the app to render black screen. There could be many reasons for the camera showing the black screen, but as you said the camera was working on the previous version and stopped working in the newer version when you added an extra language, the reason could be a bug added due to the extra language. As you tagged the project "Unity 3D", I can help you solve the bug if the app was developed in Unity3D and you have the original project/source code from which the app was built
Although you put a short description but here, let me give you a glance of what I will do for you:
1) Debug the app on my local machine.
2) Narrow down the problem.
3) Make changes in the source code to fix the bug.
4) Perform thorough testing of the full app with the new changes.
I can't write everything in detail here, so let's have a discussion soon!.
For my experience. I've been programming in Unity3D for 2 years now, have worked on a some solo projects as well as a project in an indie game studio. You can check out my work here:
https://www.freelancer.com/u/bawarkhan