4K refresh rate is terrible I have a LG 27UD68P 4K on my MacBook Pro 15" Mid-2015. I can't get it to run on 60 Hz. Its only 30 Hz.

According to this Apple page its possible to get 60Hz. https://support.apple.com/en-us/HT206587

I have tried connecting two cables (Mini DisplayPort -> HDMI) but it still won't work. 

What am I doing wrong? Any advice to get this thing at 60Hz would be amazing.
I got it to work with my MacBook Pro 15 Mid-2015 using a single cable: Mini DisplayPort to DisplayPort. 

The refresh rate is 60Hz - it looks and feels amazing. No jagged and delayed movements anymore.