Hello and thank you for choosing justanswer.
You have a BRAND NEW Desktop PC, and its SLOW???
Have you the option to return it for a replacement or refund?
Did you build the PC yourself?
Where did you buy it?
Typically a computer wont even turn on, with a defective CPU (Processor).
So I find that hard to believe, that a computer guy would tell you that the processor was not good.
The way we troubleshoot things, is by replacing parts with KNOWN-GOOD (meaning we know the parts work) pats until the problem is resolved.
Do you have access to another different Processor, that you can swap out, and see if it helps speed up the computer?