What makes an editing PC fast - good video card (gpu) or the processor (cpu)?

Eskuvo

I want to upgrade my computer. I am running a 3gen i7 processor a geforce 1050.

I find that lightroom is slow when I scroll through photos in develop mode? Faster rendering in develop mode would make my editing faster...

What should I upgrade? Processor or the video card? I would like to hear opinions from photographers or videographers who have done the upgrade... I already upgraded the hard drive to ssd.

Thanks a bunch!