How can I fix my yard when it become bad?

My yard was so greeny and it looked beautiful until I started to work for Rover as dog boarding almost 3 years. It gets worse and I can't keep up to keep grass. There were lots of dogs to pee, poop and play fetch to damage grass. Also, there are more insects and worms in the soil. Now yard looks more soil and muddy. I'm not happy with my yard. I can't afford to buy fake grass - too expensive and my yard isn't great level. Do you have any ideas or suggestion? Thanks.