Check to see if the dead turf pulls up easily and look for grubs.
Check for a disease.

Here is a link that might be useful: Got disease?

Where do you live?
What kind of grass do you have?
How often do you water and for how long?
Do you have a lot of shade over the lawn?

My grass is Fescues and half shade, each day 5 min.

dchall has this one.

pH tests on my lawn pH is 7.7 - 9.9 . What can I to do ?

Get a formal test. That pH you gave ranges from reasonable-but-high to the pH of soap.

What can soap ?

Where do you live? Earlier this week I made the assumption that someone in Zone 9 lived in the south, but she lives at the same latitude as New York City.

I live in Arkansas .

Sorry, I forgot to ask about your watering again. How often and how long do you water?

I water my lawns for 30 min. each days .

Frequent watering is very likely your problem. If you have temps in the 90s every day, then you should be watering once per week. If you have temps in the 80s, then once every other week.

Put some tuna or cat food cans around your yard and time how long it takes to fill the cans. That is your target time for watering no matter what the interval. When you know what that time is, then start to wean your lawn from daily watering to weekly with the target time as the goal. It might take a month to get the grass all the way to infrequent watering.