That I can easily play the things from my laptop on the TV with the HDMI is clear to me, but is it also the other way around?
The other way round only with specially equipped laptops. A transmission in the other direction is almost impossible.
Possibly via the Internet, but not via cable, since there's usually only one HDMI output on the laptop.
No, no television has an output through which it can be connected to a laptop.
There's only HDMI out to input converter or something similar.
Then you also need a suitable program and the right device
I wonder why that would be impossible?