I write in C++. I had a coworker who wrote in Ruby. He wanted to learn C++ because C++ is "fast". So he wrote two identical programs: one in C++ and one in Ruby. Then, he ran both programs though `time` to determine how long each took.
His C++ program took longer.
Why was that?
He didn't write his C++ program using any efficient algorithms whatsoever while his Ruby program was well-designed. He came to me to try to tell me that C++ wasn't as fast as Ruby.
So I rewrote his C++ program. My C++ program then ran almost instantly while his Ruby program hadn't even begun reading or writing; the C++ program finished while the Ruby program was still initializing the Ruby runtime libraries.
Is C++ fast? Yes, it can be. But it's only fast if the developer understands how to make it fast.
Don't use C++ because it's "fast". Use C++ because you understand what its intended purpose is: to be close to the hardware.