Latitude 7420 1,8GHz base Clock instead of 3GHz, only 15W TDP?

Hi,
i have bought a Dell Latitude 7420 Notebook with an i7 1185G7 CPU. 
On the Dell Web it says the CPU have a frequency of 3GHz to 4,8GHz.
Also on the CPU Name itself it says @ 3GHz:

But my Base Clock is 1,8GHz and not as described 3GHz. 
That is not good, because i want to have VMs on my Notebook, and they are running only on the base speed of 1,8GHz.

Also when i make heavy workloads, i can see that the cpu stops at 15W TDP and 56°C.

In the BIOS, i set it already to "Ultra Performance". But the cpu still runs at 15W instead of 28W and 1,8GHz Base Clock insead of 3GHz.

How can i make to run the cpu with 28W TDP and 3GHz Base Clock?
Did I get a defective notebook or do I still have to adjust something somewhere?

Thanks for help!