Step one:
First draw a horizontal line and a rectangle on top.
Step 2:
Then draw half an oval on the left and right sides.
Step 3:
Draw two diagonal lines upwards in the middle to connect them.
Step 4:
Then connect two diagonal lines on the oval to form the armrests of the sofa.
Step 5:
Draw an arc on the back as the backrest, and draw two small rectangles below as the sofa legs.
Step 6:
Finally, apply a nice color and the sofa is ready.