Help in GameMaker

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I'm trying to make a Deltarune fangame and I need help learning how to code in GML
For people wanting to make a Deltarune fangame, Kris' sprite size is 18 in width and 36 in height, however ingame the sprites are scaled up by 4 times.
Question for a Deltarune fangame I might make, are the floors and backgrounds in Deltarune tiles or whole textures made for that specific room?

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