Hello!
Ok, although I am not a native speaker of English, being a graduate in English language and literature, I decided to give it a try, but no hard feelings if you stop reading after the first sentence :)
Anyways, I've been working both as a teacher of English as a foreign language and a freelance translator/interpreter since 2005. My accent may have gotten ruined due to all those French and Italian people I used to work with on daily basis, but when it comes to grammar/syntax/vocabulary skills, that is something that I've been improving with. One always has to improve his or her language skills. Even when it comes to one's mother tongue, there is never something like "I know everything about it" :)
Anyways, good luck with that interview!