I recommend thinking about this exactly like the aviation industry. The language of the skies is English only. Thus all operational correspondence is in English

I recommend thinking about this exactly like the aviation industry. The language of the skies is English only. Thus all operational correspondence is in English, all training occurs in English, all logs are in English, all commands and instructions within the cockpit are in English, all preflight checks are in English. Pretty much everything that can be recorded and/or necessary to do the job is English only. Despite that unrelated conversation among pilots can still be local language. Discussions among air traffic control off the radio can still be local language. With regards to software all things related to work and product should be English only without exception. Things related to code theory outside of the product or personal education can be local language. That provides the flexibility to do what is most comfortable for self-learning but ensures there exists a fixed standard for work. By the way, English became the language of the skies for safety reasons, not for communication purposes. Forcing English usage cuts through cultural dimensions that inhibit more honest expression by less senior people.