About the loading, I'll give you an example. (Sorry i dont remember if your game is made with unity.)
When you are at the parking lot, as you get closer to the door, you can have a trigger that start loading the next scene in a asyncronous way. That way the player dont need to wait for the load, as it loads at the same time the game is playing. and when the player enter the office, you would unload the previous scene, releasing the assets from memory.
(It's a lot of work to make it that way. so might not be the best thing to do in an in progress development. But you might want to consider developing that wayy on the next project, I myself just learned about asyncronous loading during the development, thats why i did't put in my game)
https://docs.unity3d.com/ScriptReference/SceneManagement.SceneManager.LoadSceneA...