As a 1st time homeowner, I am completely ignorant of how to deal with my lawn(s) and have a few issues... I put new hardscape in the front yard, re-did the sprinklers, and laid sod - Dwarf Tall Fescue (Festuca Arundinacea). On the areas that are shaded by a large tree, the grass is growing well (and I'm getting used to my lawnmower). On the part that gets full sun for most of the day, the growth is VERY slow and some parts are thinning. Watering is done every other day for 8 minutes on the shady side and 15 minutes in the sunny area. Another issue is in the backyard where I pulled out some old hardscape, placed sprinklers, and spread seed (same grass as in front). It has been a few months and the grass is coming up acceptably with (as expected) a number of weeds. I've spot treated the weeds to kill them (& gotten a bit of overspray on the surrounding grass). I was intending to get some more seed into these areas but would like to incorporate this with the solution to another problem. I'm not happy with the grading that was done before the seed was spread - there are places that it's easy to trip in! I was wondering if it might be work to go over the lawn with some sort of enriched soil to fill in low spots. It might be ugly for a while but wouldn't my existing grass come up through this thin topping/levelling layer? I could even add more seed at this point to help with the issue of the dead grass from the aforementioned weed treatment. Comments or recommendations?

In your region, I believe KBG and fescue are the most popular. If the old lawn is dead though, you can plant whatever you want. The easiest way to get a nice lawn is to use sod. The downside is that it is expensive unless we are talking about a small yard. If the area is larger, seeding would be the best option. The first step is to clear all the dead mess. The easiest way is to mow as short as possible and bag the clippings. Then, go back with a string trimmer and chop off everything to the soil level. Rake up the debris. If you have any low spots, fill those with topsoil and rake the area smooth. Put out your seed and fertilizer. Sprinkle a little straw over the top and keep it watered several times per day until the grass starts to grow.

No fertilizer this year....the main goal was to kill the moles and since I was a bit late I was suggested to wait till the next year to fertilize by a few people. For weeds I used Weed B Gone which killed most the weeds. I am still looking on how to kill clover which it did a poor job on killing. Was told it is hard to kill off. Total bottles used is 4 1 bottle for front and 1 for the back over a 2 month period. I used a 20 gallon sprayer @ 2oz setting as this yard was very poorly kept for many years (more dandelions then grass)

Definitely sounds like fungus and heat killed your grass. Watering at night is a no no when it's hot and humid. The prolonged moisture is an ideal enviroment for fungal disease. Tall fescue is one of the more heat tolerant cool season grasses, but not the heat you have. Also, you really can't successfully seed a cool season grass in summer in OK. I think the only cool season grass you could have success with is hybrid bluegrass. For your area a warm season grass like Bermuda, St. Augustine, or Zoysia would be the better choice.