If it's coming towards the end of the year, solve Advent of Code in the new language you learned. AoC scales gently. On day 1 if you can't see how to do it that's going to be because you didn't really understand your new language. By day 25 it's very likely that you can't figure out how to solve the problem yet in any language, if you're up for it, maybe solve it in your existing favourite and then try the new one.

Because lots of people do AoC, especially in popular languages like Rust or C++, you can see other people's solutions in the AoC Reddit solutions thread each day, which are often inspiring -- you learn new idioms, library features, or even whole CS concepts.