I wanted to know if I can deactivate my laptop except for the screen and then connect my pc to the screen of the laptop with an hd cable.
To my knowledge not with standard laptops. Just the other way around.
No, this is not intended for a laptop.
If the laptop is running, you could use a capture card to display the signal from the PC on the laptop and use it as a screen.
Of course you can (if you have windows 10) in Settings> System> Display and at the bottom you can set it.