Hi, I wanted to ask if you can connect the monitor of a laptop to my PC and then I can use it as a second monitor (possible solutions would be net)
No, unfortunately this is not possible with a cable, as the laptops simply do not have the necessary hardware. You can only output a signal, but not display it on the screen.
However, there's software that you can use to simulate a second monitor with your laptop. This then works via WLAN and is not suitable for games or the like due to the resulting delay.
In Windows 8/10 this is called Miracast. Instructions can be found here:
https://www.wintotal.de/tipp/laptop-als-monitor-nutzen/#31_So_richten_Sie_Miracast_ein_um_den_Laptop_als_Bildschirm_zu_nutzen
Unfortunately not - not even if you disconnect the laptop screen. The connections don't fit at all!
I know what I'm talking about because this thought has also occurred to me…
It would work if you disassemble the laptop and connect a corresponding driver board. An example: https://www.amazon.de/...06XKVCXM9/