You say you know, but it sounds like you don't know.
Or you're acting like you don't know.
If you want instant beautiful lawn in July, there's astroturf and there's turf and a ton of water. Turf and a ton of water gets to be an expensive habit, particularly if you get water-use restrictions while it's not established, and it drops dead or you get fined for watering it.
The time to make a nice lawn in July is October (more or less.) If you want to improve your lawn with overseeding, the fall is the time. If you'd like a happier lawn, what you could do now is add compost, raise your lawnmower cutting height, and send in some soil samples to your test laboratory so you actually know what your soil needs, rather than throwing some random "lawn fertilizer" at it. It may or may not need lime, for instance, and lime is best applied at a time different from when fertilizer is applied.