I learn one language, master it (or well, I get close to mastering it), and then I learn another. I have tried learning 2 languages at once and it just didn't work out for me. I got confused and it just made things harder. In my case, I was studying 2 languages which are similiar - Chinese and Japanese. Even though I am a native Chinese speaker, I got confused and mixed some things up. Plus it was extremely hard for me to manage my time so that I could give both languages the attention they deserved. You'll find that even if you're learning languages one at a time, it's faster than learning 2 at once and not being able to get a good grasp of either.