Overall dimensions 2.15m x 2.45m due to the headboard.
Well, that immediately expands the room size for the bed ... Room width, meaning the wall the bed is against, I would then set to at least 375 cm and room depth to at least 320, better 340 cm = 12.75 sqm
And, you can now see the problems that arise from seemingly ideal line drawings.
Start making the plan with wall thicknesses.
Graph paper, correctly draw the overall dimensions once, make multiple copies and then get going with the pencil.
And, consider the costs. I just read your statement about that in a financing thread. What is the maximum the house is allowed to cost?