How to survive in a 100% Closed Source Tech Stack?

I was hired as a lowly junior at a tech company that HATES HATES open source.

Everything is 100% developed in house. Managers ban everyone from using opensource code in their projects even permissive licences like BSD or MIT.

Tech Stack is as follows:

Custom programming language like C++ but higher level

Custom compiler for their custom programming language, written in pure C

Custom VLIW processor for DSP and GPU tasks, with their own instruction set architecture (They do ASIC design themselves)

They said they designed this way because they can optimize the entire tech stack and make it have faster execution times than their competitors.

Whenever I have a problem like the code doesn't compile, I cannot google it or use ChatGPT at all! It returns exact zero results. The documentation is very poor for their programming language and compiler.

I basically have to spend like 90% of my time reading the compiler code or code for their custom libraries to understand why it doesn't work.

Anyone have the same problem?