If I could only use one language I'd pick Haskell. I've been using haskell for about 10 years now, and I'm certainly not blind to it's weaknesses, but I still generally find it to be a joy to work with and, from a practical standpoint, I find it to be an incredibly versatile language that can be a good choice for a huge breadth of different real world problems. Perhaps most importantly, I can't think of any other language where I spend less time dealing with problems that aren't directly related to the problem I'm trying to solve.
If I get to pick a second language I'd probably pick Rust. Although I have much more experience with C, and I've only started learning Rust recently, it seems to fit the same niche as C for most problems while offering the benefit of a more expressive type system and much better memory safety in the general case.
We're a place where coders share, stay up-to-date and grow their careers.
We strive for transparency and don't collect excess data.