Wow, amazing! How long did it take you to pick up all these languages?
Well I knew most of them already somewhat last time I listed them off in this forum which I think was 7 years ago. But I learned the Nordic languages and Italian since then and brushed up on all of the ones I listed off if they were languages I used most often. So about 7 years to add new languages. Once I learned a few different ones I carry the aspect of linguistics across them all to help me speak (and read, which I'm better at since pronunciation is the most difficult of this mix of languages).
The way to go about it is just to do it, you only live once and well it's worth it to learn to live it up a little also to travel and use language skills!