1. Initial Room Setup

Step 1: Set up the basic shape
Open Blender and delete the default cube.
Add a cylinder (Shift + A → Mesh → Cylinder) to serve as the basis for your room since your sketch shows a circular structure. Set the number of sides to a reasonable number (e.g., 40) for smoother edges.
Scale the cylinder along the Z-axis (S → Z) to create the walls of the room. You can also scale it overall (S) to match the size you want.
Apply the scale (Ctrl + A → Apply Scale) and Shade Smooth.

Step 2: Create a round window with Boolean modifier

• Now we’ll create the cutting object, which is a solid extruded circle.
  Add a Circle. Extrude the Circle to Make It a Solid Object.
  Press Tab to enter Edit Mode with the circle selected. Select all vertices of the circle by pressing A. Extrude the circle along the Z-axis by pressing E and moving your mouse upward. This will create thickness and turn it into a solid object.
  You can scale it along the Z-axis (S → Z) to make the extrusion as thick or thin as you want. The goal is to have a solid shape that passes through the cylinder wall. Return to Object Mode.
• Apply the Boolean Modifier
  Select the Cylinder (the wall). Go to the Modifiers tab (wrench icon). Click Add Modifier and choose Boolean. In the Boolean settings: Set the Operation to Difference. In the Object field, use the eyedropper tool or select the extruded circle as the cutting object. Apply the Boolean Modifier.
  After applying the Boolean, the cylinder should now have a round hole where the window is. If you go into Edit Mode (Tab), you should see a clean cut where the extruded circle was positioned. You can now delete the extruded circle.
  Refine the Mesh (Optional).

Delete Wall Faces: Start by selecting the wall faces where the exit corridors will be placed, and delete these faces to open up the space.
Extrude Edges for Corridors: Select the edges around the deleted faces, and use the extrude tool to extend these edges outwards, gradually shaping them into curved corridors. Adjust the angle and direction of the extrusion as needed to achieve a smooth, natural curve.

Extra Tips:

• Smooth Shading: If the cut-out window edges look jagged, switch to Edit Mode and use Subdivision Surface or Smooth Shading to refine the appearance.
• Adjusting Geometry: Sometimes after the Boolean operation, the mesh might have extra edges or vertices. You can go into Edit Mode to clean it up and ensure everything looks smooth.

3. Creating a Stained Glass Window Effect

2. Creating Window Cushions

• Step 1: Basic Shape
  • Add a new cube (Shift + A → Mesh → Cube) to create the sofa.
  • Subdivide the cube (Right-click → Subdivide) to add more geometry that will help when shaping the sofa.
• Step 2: Refining and Smoothing
  • Use proportional editing to adjust the sofa so that it fits the round wall and looks smooth.
  • Apply a subdivision surface modifier to smooth the overall shape (Modifier Properties → Add Modifier → Subdivision Surface).
  • Use the loop cut tool (Ctrl + R) to add cuts for better control of the curvature.
• Step 3: Cushion Detailing
  • For the cushions, duplicate the base of the sofa and use scaling and extrusion (E) to define the cushion volumes.
  • You can use a cloth simulation for finer cushion details if desired or manually sculpt the cushions in Sculpt Mode.

4. Modelling Geometry Lamps

5. Modeling the Chairs

• Step 1: Start with the Base Shape
  • Add another cube or sphere and scale it into the general shape of the chair (as per the smaller sketch on the left).
  • Use extrusion to model the shape of the seating area.
• Step 2: Chair Back
  • Add more geometry through extrusion for the backrest. Scale and curve it to create the organic, flowing shape of the chair’s back.
  • Apply a Subdivision Surface Modifier to smooth the chair, and use edge loops (Ctrl + R) to sharpen any edges that need to remain crisp.

5. Modeling the Coffee Table

• Step 1: Organic Shape Table
  • Add a plane (Shift + A → Mesh → Plane) and enter Edit Mode. Subdivide it a few times to give you enough geometry to work with.
  • Use proportional editing to create the wavy, organic shape of the table.
  • Apply a solidify modifier to give thickness to the table.
• Step 2: Legs
  • For the legs, create separate cylinder objects. Model them individually by scaling and rotating them to match your sketch.
  • Position them under the table.

Process: