How do I fix this yard?

You can use mulch or gavel to fill in the blank spaces.

I’m not sure whether your green is something you’re trying to get rid of, or is the green made from concrete or if there are pavers under it. You have a lot of pavers around it. Maybe you can do something with them. I would see whats under and rake and smooth the ground. You could use them to form a little patio or fill the hole in the green and use it for some seating.

I would build up the "green" and grassy area so it was level (use the pavers to build a low retaining wall) and put in grass, shrubs and flowers.

Just throw some grass Seed out there

I would get some more of the green and make the whole backyard a put put course for the grands. That's what I'm doing with my backyard. I never use it for anything else so that would be the best thing. Old wooden buckets for traps on the course, an old head from Halloween someone got rid of that opens and closes it's mouth. A little windmill. The options are all in the imagination. Ultimately it's up to you. I have 9 children of my own and expecting a grandbaby soon. So the kids rule my backyard. I just think it's a cute idea. And cheap. Good luck.

You could use the bricks around the grass to improve the edge of the patio. Then level out the dirt space (either by loosening the soil and raking or getting a load of soil). Afterwards sow creeping thyme which is low care. You can walk on it and it rarely, if ever, needs mowing.

Thanks.