Premiere Pro - laggy playback / slow rendering - what to do?

Hi folks,

I surfed the internet for some answers to my problems, but still not satisfied with what i read
Right now I am using the latest version of Premiere Pro and for some reason preview/rendering is taking ages in my opinion.
Before I was using a AMD system that absolutely sucked, Now recenlty I upgraded/bought a new pc and there is not much improvement to be honest.

My new/current PC specs are:
- Windows 10 64bit
- Intel i7 6400k (4 cores, 4ghz / 4.2 boost)
- 16 GB ram [2x 8GB ram (2133mhz) DDR4]
- MSI NVIDIA GeForce GTX 1080 8GB
- 480 SSD Kingston (Sata III)

From what I understand is that for Premiere Pro the CPU does most of the work.
Obviusly it's not the best CPU out there, but I have to say I am extremely dissapointed with the performance of Premiere Pro combined with my current system.
Whenever I'm editing Full HD footage the playback becomes very laggy, and these issues increase with every step I take.

I am not using any effects on the video tracks, no weird video/audio plugins. [It's just raw footage.]
With every slice the playback becomes laggy again (can't work with it when using live playback) So I  have to render all the edited parts over and over again.

Is there anything absolutely wrong with my system? Or perhaps my settings in Premiere Pro? (i've tried several settings I found on the internet, changed some stuff around but nothing seems to work or improve the render quality/speed)

Right now all that seems interesting enough is to edit 'offline' and that's not something i wish to do.
I really hope someone out there can help me out, and tell me what i am doing wrong/is wrong with my system.

I hope to hear from you

René
The Netherlands.