English, fluent reading at least, is absolutely must have for a CS person.
There is a huge difference between, say, Indian guys being taught in English and Russian being taught in Russian.)
And, of course, never read any serious books, like TAOCP or SCIP in translation.) Master your English first and then enjoy non-distorted flow of author's thoughts in his own wording.
how? the world's ranking of english proficiency is dominated by Europeans https://en.wikipedia.org/wiki/EF_English_Proficiency_Index#2... I am pretty sure among the IT branch the scores are much higher although you don't need perfect language skills to understand technical concepts.
While you don't need perfect language skills to understand technical concepts, not being at full proficiency can be a barrier. I know that when I help people out on StackOverflow, one of the main barriers to answering some people's questions is that they can't formulate it in English in a way that I can understand. Proficiency is a two-way thing; besides being able to read English, you need to be able to speak and write it well to fully interact with the technical community.
You do notice they aren't recently startup-famous in any way, right?