What language to teach theory?

Question

Information Security

Somehow strange, but this question came to my mind after 5 years of work in IT and in meringue.
It is very often difficult to explain yourself in Russian, since customers are foreigners and all IB standards are read in English (I don’t work for the government)
now the question is
How do you deal with this language barrier
How did you solve the problem of a competent vocabulary
Because, for example, I know a lot about IPS but half of the terms in English
Or, for example, about PTES (penetration testing execution standard) I can only tell you in English ,
stages, etc.
What should I do, security citizens?
UPD: Since the local natives do not understand the meaning of the question, I will rephrase
Do you consider it necessary to know the theory in several languages, adjusting
1) for the customer and know everything in English
2) for the needs of colleagues, although it is minimal, and learn everything also in Russian

Answer 1

It is better to know 2-3 languages. At least at the level of a confident user