Question about the proportion

Hello everyone In my current project consisting of simple primitives, I failed to keep the proportions.Therefore, I wanted to ask for advice on how to make the roof and door proportionally.

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One thing that could help is to add a reference plane inside Blender. In the “add” menu, you choose
image → reference and you will have your image on a plane inside Blender. Then, you can model it side by side with the image and compare as you are doing it.