One method that works wonders is Michel Thomas’ method. I have no affiliation with them, just personal experience. The method feels weird initially (old man’s audiotapes), but if you had slightest interest in neuroscience, you’d see it’s absolutely brilliant way of tailoring the learning to how the brain works.

I can read newspaper or have a brief conversation in a restaurant or shop in ~6 languages. You can acquire that skill easily in ~20 hours of audio (per language). But the course stops at certain level, and getting to active speaking is still very difficult next step.