I can make myself understood in three languages total (Finnish, English, Swedish). This goes all the way from understanding fairly technical/detailed vocab to being able to explain things and understand most of the things expressed to me in everyday communication. My issue is that I have attempted several others (French, Greek, Spanish, Italian & Russian) without mastering any of them due to lack of discipline and just general overwhelmingness of grammar.
How my type might influence it; when I reach for le mot juste it may not be the most accurate or precise one but the one that feels right in the moment to convey the message, with nuance going into the meaning, interpretation and intent more so than technicalities... so less about going by what the dictionary says and more "how will these words be taken in -- by whoever is listening?" That said, I would prefer to use a word in the form that is comes to mind, be it in whatever language in that specific moment, as it seems poetic and fitting and expressive and descriptive to do so... the downside is that each word in a sentence can emerge in a different language. Then truly it takes a translator to figure out what is exactly being said. So I try and resist the temptation to do so as it might confuse others as well as myself.
Plus I find some languages more liberating or suitable for expressing something specific. I see different "purposes" or natures to them. Russian requires a whole different way of thinking because time and actions are understood differently... English has the greatest selection of words to choose from and each has a pretty precise meaning to it so it is great if you want to be specific... Finnish has a relatively free way to organize a sentence so you can just say and write however you want so it is naturally great.. etc.