I have tried to make blender faster by using my Nvidia GeForce GPU in the user preferences window and under the render options in the properties window. But I can see in the task manager that the CPU is used mostly and even though it is set on multiple tiles it is still using only one. How could I increase the GPU usage and the amount of tiles? Thank you for the answers:)
Switch on GPU compute in the task manager. That will show you something else ;-) GPU compute is different than realtime rendering to task manager. It shows 97% to me while GPU 3D is barely working.
Go to GPU click on one of the sub diagrams like copy and select compute_0 or 1 or whatever yours is called.
be aware that you need something like 1080 before it is faster than a modern day cpu with 4-8 cores.
As your main goal behind this question is to get faster renders, then it is worth checking your tile size setting --- this can make a big difference.
CPU's generally like smaller tile sizes (e.g. 32 or 64) and GPU's large ones (e.g. 256 or 512).
You may wish to try the Add-on "Render: Auto Tile Size", which you can enable from
File > User Preferences > Add-ons
Also, your CPU might still be faster if your GPU is not that high end. On my system, my 8-threaded CPU outperforms my GPU with CUDA, probably because it's an older model and a laptop. My video card is a combined Intel/Nvidia (bumblebee)
Unless, I just didn't use the right settings... But I noticed 8 tiles at the same time rendering through the CPU and only one with my GPU