Hi 
Ahh, i forgot that you haven't got a lot of experience with ODFAuthors. Hopefully someone can set-up a login for you. These guides might help a bit
https://wiki.documentfoundation.org/Documentation/Development#First_steps_with_the_Documentation_team
Although the whole wiki could use a bit more work as always so if something doesn't make sense feel free to ask. People do work quite hard at the wiki but it's the sort of thing that needs constant work.
Your English seemed fine so don't worry about it. Just get straight into adding the things about new functionality and stuff. There are always others that can proof-read and review your work so don't worry.
Since quite a few people have expressed interest in working on the Calc Guide it might be good if you each sign-out one chapter each and then review or proof-read someone else's or work on a new chapter if there isn't one already signed back in by then.
There is always a longer-term member of the team around to do final proofing and stuff so don't worry. The aim is (again) to get the 4.0.0 guides out quickly and then perhaps worry more about the quality next time. "Release early and release often" although this team seems to release more often than seems possible.
Regards from
Tom 