Honestly, the best way to improve at speaking the sort of English that you would actually use when talking to people is to use English to talk to people.
You may worry about doing that, but what you wrote there is completely understandable by anyone who speaks English natively, even if the grammar isn't perfect and the word choice may seem a little off. Those are things that come with time.
I'm not sure if you're still living in Japan. If you aren't (or even if you are) you can probably find people around to speak English too. And even if you can't, that's what this website is for. I'm a little bit busy with projects and exams at the moment, but I'd be happy to speak with you once I'm not (around April or May). I know a little Japanese (although probably far less than you know of English).
One thing I've noticed every time I've met Japanese people trying to speak English (we had a lot of exchange students come to my high school) for pronunciation, is that you try to use katakana in order to pronounce English words with Japanese sounds. I recommend very strongly not to do this, if you want your English to sound more like a native speaker, as English has a lot more sounds than Japanese, and it's important to be able to reproduce them, not just imitate them as closely as the sounds in Japanese allow.
I know your question is more about vocabulary, but I think the pronunciation is an important thing for any Japanese person learning English (it's definitely not your fault, it's more to do with how English is taught in Japan in general, which is changing but slowly).
But like I said, I'd be happy to do skype calls or something when I'm less busy, and until then if you'd like to write me messages, I can try to correct them so that they sound more natural.