[checkyoursudo]

My primary language is English. As a teenager and into my 20s, I learned German. As an adult, I learned French, then Attic Greek, then Latin, then a bit of Hebrew. I started with some Mandarin, but I didn't go far in that. Now I am learning Swedish.

I have found that my ability to learn a given language has been almost entirely independent of any of the other languages I've learned. At least that is my perception of things.

I learned German really well -- that is my most proficient besides English. I don't especially feel like learning German helped me much with learning any of the other ones or now while I learn Swedish.

Edit: Nor do I think that learning multiple languages has hurt my ability to learn more, for whatever that is worth.