What do you mean by ''if I finish the places in a room there's the possibility to use the other tables''?
In other words, you are trying to physically move tables from one room to another?
1) If room 1 is full and room 2 has tables available, do you want to physically move tables from room 2 to room 1, as there is still space available in room 1?
2) Or do you want to be able to make the customer book a table in another room when the availability of a room is exhausted?
1) The solution in this case would be to go to Configuration > Dining Areas, copy the tables you want to move from the blue button, select the tables you want to move to the other room and click the orange Move to another Area button (PIC8).
To have them available at all times without affecting the real availability of seats, you can deactivate the tables by clicking on the appropriate button (PIC7), when you physically move them to the other room, you can decide to reactivate them .
2) If you want the customer to be able to reserve another room when a room is full go to Configuration > Dining Areas and in the top right-hand corner you will find the Availability settings tab, under Availability out of stock select Error.
In this case, if you have allowed the customer to choose the room (Configuration > General Settings > Allow the customer to choose the room) the customer will only see the available room to book.
If you have not activated this option, the customer will not see the availability of the rooms and will be directly placed in the room where there is availability.