Finally figured out how i could open severeal Diablo 3 Games on the same computer
First thing find your installation of Diablo 3 in my case C:/program files/diablo 3
Right click on Agent.db and click open with now chose for example Notepad
when u have the text on screen u need to find a sentence that says Support_multibox : False
Change FALSE to TRUE. And save the file.
Now find your Battle net installation folder in my case C:/programdata/battle.net
There should be a folder named AGENT Delete this folder.
All this worked for me and now i can use my 2 characters together to farm