Swift can be just as fast as C or C++. The danger, in my experience, is that it's not always clear what the performance implications of the language's many convenient abstractions are. (A random example, I recently improved one code path by over an order of magnitude by replacing some serialisation that used Codable with hand-rolled code. Still 100% Swift, just paid a lot of attention to avoiding RTTI and allocations.)

Swift had automatic memory management, so yes ()

(: Although anything can be made as slow as python yada yada)

A bit slower is good if it is safer from exploits than C and C++.