[Catyoul]

Armenian and Farsi : Native speaker, but now mostly forgotten. It would come back in two weeks if needed though. I never really knew how to write/read them though.

French : Native-like. Learned it when I arrived in France and has been my main language since then.

English : Fluent. Started learning it one year after French, and it developed over the years.

Dutch : Good, but no more practice. Started learning it one year after English, when I went to Belgium and developed a good level. I've left Belgium for 9 years now, so it's mainly gone, but could probably come back quickly.

Latin : Fair and forgotten. 6 years, excellent level at the time, I used to speak it sometimes with a high school friend of mine, but I won't get back into it ever again I guess.

Arabic : beginner.

About the thinking process when you're fluent in several languages, it depends on what you're using the most at the moment, the environment you're in at that moment, and what you're thinking at. You may be thinking of one subject in one language and when switching to a subject where you have much more experience in another language just switch seamlessly in your mind as well, or even mix them.

It also appears to help a lot to have learned 2 mother tongues when learning new languages.