Ok I see it now. Thank you for your help!

Yes thats the one.
On the booking page you will see: Price shown for occupancy is 2 people. And when you click 'book' it will also show occupancy for 2 people.
This should be 3.

While making the rooms i've set maximum guests to number above 2 and the rate concerning these rooms are set to a room price per max. room capacity. Still, the booking page always shows 2 people as max occupancy.
I need help please how to resolve this.