simple start is adding native clover and dandelion to the grass (and obviously not spraying herbicides or pesticides)

• clover adds nitrogen (and was a traditional part of lawns up until WWII)
• dandelions attract pollinators and every part of dandelions are edible
• don’t trim/mow shorter than 6" (15cm) – triggers grass grazing response rather than damage response
• once that’s established, then you can move onto planning and design
  • native wildflowers, bunching grasses, erosion control, vegetable garden, fruit trees
  • for a garden area, the turf can be flipped over for a basic sheet mulch starter

Sounds lovely, I'm sure folks here would be delighted to see progress pics as you're working on it!