My Unity freeze

Hello everyone,

I have a problem with my Unity, when I want to modify a wall with ProBuilder, subdividing it, or undo an action, It freezes for 10s or even 30 / 40s.

My processor does not exceed 12% on Unity, and my RAM 800 mo. See picture:
https://nsm09.casimages.com/img/2019/09/12//19091202002924717716405523.jpg

I give you the details of my PC:
Windows 7 Pro x64 Service Pack 1
Inter I7 2600K 3.4 GHz
Motherboard P8H77-V LE Rev X.0x
16 GB of DDR3 at 667Mhz
NVidia GeForce GTX Titan 6GD 5 GK 110 at 324 MHz - 6GB of GDDR5

For information, I just installed, I do not make any changes with "mod" or external file. I only installed PRodbuilder via the PackageManager.

Can you tell me if :
- it is possible to allocate more ram?
- to allow multi-core operation? (because I feel that there is only one core that works on both Unity)
- to allow the operation with DirectX / OpenGL, finally the graphics card what?