Sometimes, bumps are just air pockets. Stab them with a pitchfork. Seriously. Push a garden fork deep into the bump, then wiggle it. You’ll pop the air bubble, and the bump might collapse on its own.
If it doesn’t, pour water into the hole you just made. Let it soak in. The water will wash soil into the void. It’s like giving your lawn a colonic to fix its posture. It sounds weird, but it’s surprisingly effective.
How To Level An Existing Yard at Charlotte Mcgowan blog
What About the Low Spots?
Big dip? Don’t panic. Use a shovel to cut a "H" shape in the turf over the deep area. Peel back the grass like a slice of pizza. Add dirt underneath, then press the grass back down. Water it well. In two weeks, you won’t even know you performed lawn surgery.
Fun fact: the average American lawn has 7.3 hidden trip hazards per 100 square feet. I made that up, too, but after you start looking, you’ll believe it. Your lawn is basically a game of minefield.