I always look for ways to improve my English writing skills. But I don't like the learning apps like Duolinguo and such, because I got the feeling of being dumb.
Here Idiomcoach use what I write in emails or on Github PRs to make me progress and correct my mistakes.
It improves everyday and it fits with my professional life. I am not learning sentences like "The cat is sleeping on the monkey"...
It can definitively help if you have an international team, or if you contribute often to open source projects.
Typeform