I want to play the 2nd screen of my Wndows 10 laptop wirelessly on the RaspberryPi, for example a PowerPoint presentation.
Remote Deasktop just the other way around. In same network.
Model 3B +
You could install a VNC server on your Windows laptop.
eg https://www.realvnc.com/de/connect/download/vnc/windows/
And then connect with your Raspberry with a VNC client to the server. There you would have to be able to see and control the screen live.
Does the vnc server not need a license?
Take UltraVnc is open source and free.
Vnc or if you have the Professional version of Windows 10 you can use the Remote Desktop.
And on the Pi with vnc viewer, right?
Yes, I would give it a try.
Remote Desktop with what software on the Pi?
I have 10 per win on my laptop
Remmina should support RDP.