M340CLZ Resolution setting issue

[Basti2000]

Hello Guys,

I recently bought a new monitor: M340CLZ by microboard
http://www.ebay.com/itm/M340CLZ-34-034-WQHD-3440x1440-1...
So now I have the problem of my Pc/monitor not recognising the right resolution of 3440x1440 all the time, instead it sets 2560x1080 for the maximum. Restarting my monitor SOMETIMES works and the resolution automaticly snaps back to 1440p. Most of the time Im stuck reconnecting and restarting my pc and monitor in different combinations. (monitor first, waiting 'till the pc is booted up etc.). Most of the time I get it to work within 10-20 minutes (everytime I start my pc). So my questions are: 
Are there any known issues with this monitor/graphics card like this ?
where does the pc know from which resolution my monitor is capable of? Does the monitor send the information everytime its started ? Or could it be an error by the notoriously bad AMD graphics driver   ? could it may be that my windows isn't activated right now ?

Im using the DisplayPort cable that came with the monitor btw.

My other system specs are:
Intel Xeon E3-1231v 3
AMD Radeon R9 390X watercooled 
Gigabyte z97 g.sniper Motherboard
Windows 10 

Sorry for any bad spelling or grammar. I'm not a native speaker  
Thanks in advance
Basti