Welcome to the site!
If you are referring to the text in your forum posts, you can access different fonts and sizes by checking the "rich text editor" box on your profile page. This should also let you change the font in your stories as well.
I'm fairly certain the site is only available in English, though I could be mistaken.
Most people tend to do editing on a case-by-case basis, so when you're finished something, post a link to it in "writing workshop", and whoever has time might read it over and give feedback. However, I recommend fixing all spelling/grammar mistakes in your work prior to sharing it, as most editors don't like dealing with that.