please check the audio tab in the settings and the advanced audio mixer
look that the tracks are set right
you can post here a screenshot
Here are a couple of screenshots. I tried many thing. Now one question I have is whether it matters what microphone I use. Do the apple headsets with a microphone integrated in them good to use? I assume they would.
Another question is, when I open OBS, in the audio mixer, there is alread 2 things present: Desktop Audio and Mic/Aux without having any sources added, is this normal? (screenshot added as well).