These English phrases and words are also written in devanagari. They are a natural part of the language, almost like Sanskrit, Persian, Tamil, Arabic and other loanwords are part of Hindi. If you want to speak naturally like a native speaker, you need to use them too. If you read modern literature, they will also appear. In more classical literature you can find more Sanskrit words for example. I know very little Hindi but I can speak and read more Sanskrit and I can say that Sanskrit helps quite a bit to learn Hindi although English helps a lot too for modern conversations.

Young people sometimes also write Hindi and Urdu in the Latin alphabet when they're chatting or using social media.

That's the English word 'school' in Hindi स्कूल and the Sanskrit word would be विद्यालयः

In Hindi you can also use the sanskritised word but the English word is more common now and current textbooks teach the English word for 'school' in Hindi. It's also important to get used to the Hindi pronunciation of some English words in Hindi and to match them with the Hindi prosody.

You said you were looking for ब्रह्मास्त्र - I hope this helps:

Is that what you were looking for?

I'm also hoping for Hindi to be added soon. I'm using Assimil for Hindi.

Assuming Hindi will ever be added, you know what they say about assumptions, right? Lol No offence intended 😉

This seems to be quite a normal thing in multilingual countries especially when one of the languages is a world language like English. I know that in South Africa English and Afrikaans are often mixed in normal conversation. Even in English many foreign words are used naturally, especially French and even quite a few Hindi words. I believe that in India educated Indians have assimilated many english words and phrases and these are used in a very natural manner as part of day to day language.

Whether this is a good or bad thing I cannot comment!