IMHO most languages are fairly similar to one another. Once you understand the underlying concepts and paradigm-level ideas, syntactical differences are pretty trivial to pick up.
What slows you down is when new ideas are introduced, like when you go from multi-paradigm languages like Python & Typescript to a more purely functional language like Haskell, or learning about ownership in Rust where there may be no equivalent in other languages. But ideally you only need to learn them once, and in a way that allows you to identify and apply them in a variety of contexts.
This past week I set up our project's Azure DevOps wiki, uses markdown and allows you to generate graphs using mermaid.js - very nice, especially since it's harder to blackboard ideas remotely. Although we were initially just using a README file, it's faster to contribute to the wiki and is easier to manage more information with it.
But regardless of whether you have a fancy doc site or just a single README, I think it's important to just get information down that's actually important and written as clearly as possible, and then sorting by how commonly that information may be needed. It's also helpful to put yourself in the shoes of a junior developer or someone completely new to the project: does x make sense outside of this context? Oftentimes when we refer to some project-specific concept, we don't realize that there are implicit mental dependencies that someone must have before they can understand what we're talking about. The best documentation makes the fewest assumptions they can get away with about the reader's previous knowledge.
There's an app you may enjoy called Loop Habit Tracker. I used it to keep track of streaks for things I couldn't as easily track through other means. Its pretty amazing how just seeing your streaks can be so effective in building habits.
What slows you down is when new ideas are introduced, like when you go from multi-paradigm languages like Python & Typescript to a more purely functional language like Haskell, or learning about ownership in Rust where there may be no equivalent in other languages. But ideally you only need to learn them once, and in a way that allows you to identify and apply them in a variety of contexts.