People often choose to use C++ because of it's performance, willingly sacrificing programmer productivity to the alter of language; tool-chain and application complexity to do so.
Then they inexplicably decide to use strings everywhere; with bazillions of dynamic allocations and memory copies, recklessly discarding any shred of hope that they might have had for, y'know, performance.
If you want to do a ton of unnecessary string manipulations & memcpys your application is going to be slower than it could be, regardless of the language it is written in. If you want performance, the programming language that you use is literally the least significant choice that you can make. What you chose to do is far more important than the language that you use to express those operations.
Also, the word "fast" is totally and utterly meaningless; to the point of being dangerous. What a database developer means by "blazingly fast" is totally different from what an embedded engineer, or a VHDL developer means by the same term.