In most big tech companies worldwide English is a working language. Even in Google or Amazon offices in, for example, Germany or Japan most of the work and everyday communication happens in English. This way people from other countries can work there as long as they know English well, without the need to learn German or Japanese.
Almost all software engineering interviews are also conducted in English. Therefore, it is super important to know English well enough to understand it and confidently speak with other people.
If you are not a native English speaker, learning the language well may take years, so start early. Here are some tips for getting your English better for the interviews:
In the interviews, you are expected to understand most of the things that are written or told to you. You are not expected to have perfect pronunciation or vocabulary, but you should be able to clearly explain your thought process and your solution.
The best way to get your English better long term is probably to take some English learning courses. There are a lot of them in most cities nowadays, but because it will take quite some time, you are better off starting earlier. Even a month or two of English lessons can greatly improve your knowledge of the language and help to avoid some common mistakes.
Get used to using English every day. Switch your phone and computer to English, google and read everything in English (content in English is usually the best anyways), watch videos on YouTube, movies, and TV shows in English with the subtitles. This way you will automatically pick up a lot of the language.
Even if your English is good, speaking with somebody in English in real-time can be intimidating if you are not used to it. Speak in English as much as possible, even if just with friends or with yourself. You can also do some mock interviews in English on Pramp with strangers from all over the world. This can help you a lot with understanding and speaking English, as well as with the interview skills.