Hello, I assume that this is a 15 inch model. I have briefly looked up the specifications: https://support.apple.com/kb... - I will base my answer on this. Via HDMI, you will only get 4K at 30Hz with this notebook. It works, but for it to work smoothly as usual, you need 60 herz. However, you have a Displayport 1.2 connection via the Thunderbolt 2 port. In theory, this can handle 4K with 60 hearts and, to my knowledge, also with this MacBook. You can now buy a Thunderbolt 2 to Thunderbolt 3 adapter and then use the USB C cable (included with the monitor) and you should get 4K with 60 hearts. Alternatively, you should be able to use a Mini Displayport / Thunderbolt 2 to Displayport cable to run the monitor at the same resolution.