I don't think it's really possible to learn a new language unless you have to. Sure, you can learn some words and grammar from books and games like Duolingo, but you'll never really learn the language if you don't use it, and you'll only use it if you have to. This is why it's hard for English natives to learn another language: too many people speak our language already. And now people won't be learning computer languages any more either.
You can absolutely learn a language even if you don't need to. But it's just a lot harder.
I have done it and know many people who have done so too. It's frustrating and slow, but if you figure out a system that works for you, you can do it.
How do you stop people speaking to you in your native language?