Use laptop webcam for PC?

Is that possible somehow?

No problem as a laptop is a PC.

No for another PC

That's another question. Usually this is not that easy to do. The easiest way would be if you make the cam of the laptop accessible in the local network (IP-CAM) and then reintegrate it into the target system.

Ok super thanks!

No, you can't.
However, you have the option of using your smartphone as a webcam.
See e.g. B.: