To those who learn English as a second language:
by the Preservation of Diversities
While master your English you are expected to be a master of your native language already!
English is not a substitution for your native language. Far otherwise.
You need them both:
1. Your mother tongue – to enrich the fabric of human community …
2. … and English – to communicate with your mates, the inhabitants of this miraculous planet.
Oil them both.
Do not give a chance to any of them to get rusty!