To speak with foreigners while traveling or to use the language in everyday life, my level is enough for me. But this is obviously not what I need for serious, business communication with business partners.

I guess it's easiest for you to find online business English courses. It's always a special vocabulary, different communication scenarios, and it's better to learn it with an experienced tutor.

Business English is a completely different level of language. This doesn't just apply to English. Any language has special business vocabulary and all that. So, promova.com has some great online business English courses that can be an effective tool for you, so it's worth a try. Check out for more information about this platform.