Hi there,
Fellow polyglot here, I've mostly studied Spanish, Russian, and Vietnamese.
Most people really struggle with language learning so I'm glad to see a post like this here. I'd like to add some notes I've learned in my own language-learning journey.
Domain: Linguistics
Link: [The Art of Language Invention, Episode 25: Ghost Segments]
Person: David J. Peterson
Background: Writer of many 'conlangs' (artificial languages) such as Dothraki from Game of Thrones
Why: 30+ part video-series about conlangs. In theory, it's meant as a resource to guide your own creation of a language. But it's also just a really good resource for absorbing how a linguist thinks about language. He talks about sounds/words/grammar, how they change over time, and what mechanisms are involved in that. IIRC he doesn't use very many tech...
<3