I have the EXACT same monitor.
Basically:
HDMI to Mini-Displayport cable would work but not at correct resolution.
Displayport cable plus the hama adapter (https://www.hama.com/00053245/hama-3in1-mini-displayport-adapter-for-dvi-display port-or-hdmi-) would not be recognized by the Computer.
Normal HDMI plus the hama adapter would work the same as a HDMI to Mini-Displayport, i.e would detect but no option for the correct resolution.
The ONLY thing that worked was (and I found this out by accident after trying to fix it for around 9 hours straight):
WORKING SET UP: NORMAL HDMI CABLE and NORMAL DISPLAYPORT CABLE BOTH PLUGGED IN TO THE MONITOR AND BOTH CONNECTED TO THE MACBOOK AT THE SAME TIME THROUGH THE HAMA ADAPTER LINKED ABOVE.
The Display option on the monitor is set to DisplayPort. You can get there by going to the moniter menu and choosing the input (click the monitor button, then choose menu on the left, then click Easy control, then Input, then go to DisplayPort.
Like I said, I have the exact same moniter, I have a Macbook Pro and it is working FLAWLESSLY with the working set up.