I speak Telugu and Spanish, the first of which I learnt at home so I can't really speak for that. However, I learnt Spanish over the course of 5 years in grade school and 1 semester in college, but I feel that my command of the language greatly improved after I started writing and speaking frequently through the help of language and composition classes. It seems like you're already planning to speak to native speakers so that's excellent, but make sure to note down any repeated errors you make while speaking so you improve over time. You might also want to find a local meetup of language enthusiasts so you can converse with nonnatives and learn their tricks to mastering the language as well.

I've been getting into explaining different concepts in theoretical computer science. The material is a bit dense and may require some background knowledge in math/theoretical CS, but here's my recent post about proofs of functor laws in Haskell.

Edit: I'd be happy to explain anything confusing in the post.