Rendering process is very slow

Hi
I am using Sketchup 2016 with V-Ray. Unfortunally rendering process is very slow.

I have a computer with this characteristics
1.-CPU Core i7-4770 3.40, 8MB Cache , 4C78T
2.- HD SSHD 1TB 7200 RPM SATA 8GB
3.- RAM memory 32GB DDR3-1600 nECC(4x8GB) Unbuferred.
4.- Graphics card AMD Radeon HD 8490 1GB PCI x16GFX
5.- O.S Windows 8.1 Pro

I need change settings in Sketchup?