restart to learn English

So I decided to restart learning English recently. Because I have got a new job last month and it required me to use English, at least, reached a medium-high level. It really is a big challenge for me. I have not used English for many years,  even during the day's that I was a student. I didn't spend too much time in English but now I want to pick it up.

I want to relearn English systematically, start from the grammar (I think I have some basic word accumulate）, but my grammar was really a mess. So if someone can recommend me a good English grammar book, it will be very helpful!

Ok, this is today's dairy. By the way, if someone wants to learn Chinese or Japanese( My college degree is Bachelor of Japanese), feel free to contact me. I'd be very glad to exchange our skills.