This is an interesting question. I don't know about dyslexia, but the question of whether dyslexia is language independent is interesting. I think one can impr

This is an interesting question. I don't know about dyslexia, but the question of whether dyslexia is language independent is interesting. I think one can improve their command of a language with practice, as you say. If they don't encounter it in their day to day life, they can try and find ways to consume content in their target language [reading, watching, listening, interacting]. As an example, English is my fifth language. Do I use it in my physical day to day life in the country I am in? Not really. However, our internal communications are all in English (code, comments, Slack conversations, GitLab issues and comments, documentation, emails, pretty much everything). The content I consume is mainly in English as well: talks, movies, books, articles, etc. This can dramatically improve both your comprehension and your production. You can take a look at Stephen Krashen's work on language acquisition, it's interesting and matches my experience with languages (confirmation bias).