By know I mean that I feel confident enough to write programs in C++.
Since I'm working on a project in C++ and it's the only programming language I know. My question is do a learn a language in my free time when I'm not working or if I start working on a new project that requires a different language and learn in as I go along?
My question is do a learn a language in my free time when I'm not working or if I start working on a new project that requires a different language and learn in as I go along?
I would say learn in your free time. Learning the language as you go in a project puts the project at risk of failure. You may make a decision based on what you know of C++ that is entirely inappropriate for the given language but you don't find out until late in the game when it is too hard to recover from.
If you do choose to start learning another language, don't take C++ with you. I learned Java after C++ and for a while I was very unhappy because I kept trying to use Java as though it were C++. After I learned to treat them separately I was much happier and I learned Java pretty quickly.