Discuss and learn French: French vocabulary, French grammar, French culture etc.
Good luck! Your plans sound really exciting! When you say you are a translator, which languages do you translate? If you are already fluent in more than one language, this should really aid you in learning another one.
I would suggest that if you really apply yourself to learning the language then in one year your level of French will be good enough to start on the course. It may be a challenge at first, but soon the course itself will increase your proficiency. Also, if you move to Geneva several months before the course starts, you will be able to completely immerse yourself in the language and culture, which will be great preparation.
My advice would be to go for it! And keep us up to date with how you are getting on!
All the best