Which has only one jack connection.
As soon as I insert my microphone, it is recognized as a headphone.
Is it possible to change this technically or something?
Incidentally, I use Linux.
Does your laptop have nothing more than just a jack connection?
Only one
Check if this is not a connection for a headset. Since these connections have 3 or even 4 (stereo) lines / contacts, a 2-pin connector (micro or headphone) can give / receive the wrong signal depending on the position.
Usually a laptop should have several…
So at least two.
I think that the jack of your laptop for headsets is a so-called combo jack, in which the micro + headphone connections run over a plug. - See your user guide.
To connect only one microphone you need a suitable adapter, like this: https://www.amazon.de/...00KSV8YCM/