There's written English and there's spoken English.
Not to discount Jacinto Jaimez, but written is much easier as you have time to proofread and correct. Jacinto might feel it's spoken English that's the issue.
I work in a company where most of the devs are eastern European and some but clients are western(North American, UK mostly). Some of the devs have lower intermediate English but it doesn't stop them from talking to clients.
And, generally, native English speakers are too polite to point out any mistakes. So, if you have some, non-teacher, native speaker friends/acquaintances and want to improve ask them to point out any mistakes you make. They'll, most likely, be happy to help.
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