This is a highly rudimentary guide and only contains some basic ideas for how you could make a multi-floor building.
Elevator Method
The Elevator Method is probably one of the more basic thoughts on how to make a multi-floor building. This method uses the method of using different areas instead of a similar area so different “floors” will be built in areas different from each other with a camera zone over it to make sure you cannot see out of it. Start with your first “floor” and build an elevator looking room with a teleporter in the center. I would also recommend adding a sign or text that tells you what floor you are on. Repeat this for all of your floors. I will now give you two methods for creating the floor choosing method.
Incremental Choices
Add two buttons, one to the left of the door and one to the right if you want them to show you can make it but it is better to hide them. Make them say “Up One Floor” and “Down One Floor” respectively. For the “Up One Floor” button make it so when it is pressed it links to the next floor up’s teleporter with: button pressed → teleport here. Then with the Down One Floor link it to the floor below its teleporter and make it so when: button is pressed → teleport here. Make sure to omit the Down one floor button on the first floor and the Up one floor button on the last floor.
Direct Choosing
With the Direct Choosing method the player will directly choose the place they would like to teleport to. For this method we will be using the traditional popup chain, I will probably make a guide on this in the future 
. So first you need to place one button down and link it to a popup and make it so when the button is pressed, the popup will show. Then set the popup’s call to action like this:
Once you have this set up, copy this popup and link the first popup to this popup with a secondary call to action presses → open popup. Then you can make a teleporter in another teleport bay with when Channel Floor #__________ Teleport relayed teleport here. Then you can just rinse and repeat wherever you need it.
Staircase Method
I will not write this myself as there is already another guide on it which I will link here.
How to make a stairway with two(or more) floors | Difficulty 1/10
Other Resources
Alright guys thanks for reading, hope you guys enjoyed.
(Part of My Guide Speedrun)
