I agree Rust on Sololearn would be nice indeed. However there are already good resources out there. E.g. the rust book teaches Rust similar to Sololearn and I was able to learn Rust with it in several days: https://doc.rust-lang.org/stable/book/
You can also use the book in this code:
P.S. In my opinion Rust is by far the best and most genius language out there at the moment, so it's really worth learning it, even if you plan to use other languages later.