I agree that everyone has the capacity to learn languages, although it will be a tougher slog for some people than others. I’ve seen a group of 30 people, many well into their 60s and 70s, learn Mandarin through immersion. Everyone eventually figures it out. Nobody is incapable.
I learned three foreign languages through a mix of intensive small-group and individual classroom instruction (10 weeks for 5 hours a day in Peace Corps training), immersion, and self-directed study.
In my experience, language is something that gets easier, then harder, then easier, then harder. The survival phrases come together after a few weeks and you start picking up on individual sounds and words, rather than the language sounding like a wall of gobelty-gook. Then after around six weeks you start being able to independently form sentence and express basic non-canned thoughts. After that, there is a long plateau, and for me, at around six months there is a sudden revelation and I quite suddenly become fluent enough to manage daily life with few hassles. Then there is another plateau, and maybe around the year mark another sudden rush of “OMG, I get this!” and I can suddenly have fairly complex conversations. For me, it’s really tough to get past “able to manage daily life” and into “complete fluency.” I’m not sure I’ve ever really managed it.
Learning a language, to me, is a nearly entirely unpleasant business. It’s boring and hard to spend two really tough hours trying to commit a tiny bit of language to memory. The daily progress is painfully slow, there are periods where your skills seem to regress, and the initial rewards are fairly modest. It’s tough to congratulate yourself too much for finally, after weeks, being able to successfully locate a bathroom. But the knowledge you learn builds on itself and unexpected ways, and when you hit those breakthroughs, it’s really, really cool. But the daily work of it? Painful, frustrating and headache inducing. And you can’t slack or just go through the motions. You need to be using your full brain power every time you sit down to leanr.
My advice is to focus on one language first, and choose the one that you will have the most authentic opportunities to use (in the US, this would probably be Spanish.) Language is primarily a communication tool, and it’s easiest to learn when it’s used as one. Once you’ve already learned a second language, the next ones come a lot easier.
I believe a month of immersion is worth about six months in the classroom, and all classroom learning has a point of diminishing returns. But immersion alone will only teach you to speak about daily life. To build actual fluency, immersion should be supplemented by self-directed grammar study and targeted tutoring. I would meet with a tutor twice a week. During this time, we’d focus on a subject that had come up in my daily life (for example, getting a package from the post office.) We’d start with vocabulary related to the subject and a grammar construction, and continue to conversation. Then we’d vary the conversation, using the words and grammar in new and unexpected ways, combining it with my previous knowledge. You need to hit all of the stages of learning- memorization, application (drills) and integration (using it with previous knowledge in novel contexts.) Then I’d go home with a vocab sheet and some grammar drills, to be reviewed at our next session. And of course, I’d always try out what we had just learned.
Obviously immersion and private tutoring isn’t going to be a solution for everyone. I’d just remember that it’s okay to draw from a variety of sources, There is no need to go down any one individual language program. As long as you do something every day, be it listening to a podcast, writing some grammar drills, or talking to an online language partner, you will move forward.