Why can i not get the input and the output to work at the same time in windows?

I just got an 1818VSL and i love using it in Studio One 3, in there it works completely fine.

Next to that i also use my interfaces for using my XLR microphones within voicechat programs within windows just to talk with my friends. But i caot seem to get that to work anymore. When i check my levels in the windows "Sound" section of the control panel, i can either only get an output (To my headphones, chael 7/8) OR an input (From chaels 1/2 of the interface). But for some reason never simultaniously.

In other words, it's either my friends can hear me but i can't hear them. Or i can hear them but they can't hear me.

Is there something i'm doing wrong in the settings? Also as a sidenote: I already tued of "Exclusive mode" for all inputs and outputs.