Thank you very much for your help.
I couldn't have had such good explanations as you two made, even if I had a teacher to ask here in Japan.
People to ask about the use of English words are what I need most because I don't go to any school at the moment.
Questions I come up with are ususally not in a grammer book or anthing like that, and there's no other way but to ask native speakers, but it's too hard to find ones to ask such questions without going to school in Japan.
I'm really lucky that I have great teachers like you.
Again, thank you so much.