Hi again.
The DP Cable doesn't solve the problem. Now i bought an Asrock BeeBox with an i5 7200U. It has two fullsize HDMI and one fullsize DP. I'm not a big fan of asrock, but i will give it a try.
With the BeeBox i managed to switch the Displays. But it's not realy simple...
First of all i had to enable the "Blank other displays"-Options.
If "Default" is selected as output device, booth, the PC-Monitor and the TV is are used. Because of different resolutions the TV doesn't show the whole picture.
In this state i have the option to select HDMI1 (TV) and DP1 (PC-Monitor).
If i select DP1, the TV is turning off and the PC-Monitor is output device.
If i select HDMI, the TV and the Monitor turning off. I have to accept the new setting without seeing the dialog and reboot the device. After the reboot HDMI1 (TV) is the only output device.
Now the only available output devices are Default and HDMI1 OR DP.
If i want to switch to the other TV/Monitor: I have to enable Default and reboot to see HDMI1 and DP again. After this i can select DP1/HDMI again, as described before.
Is there a easier way to switch the output device? Without rebooting the Box 1-2 times?