Question
I had a new lawn installed. After a few months, brown sections and clumping appeared in various sections. Also, the lawn surface became uneven so that it was difficult to walked on it. I'm thinking that it may be old sod that had too many roots warped around the mesh that is used. The lawn also appeared to have different types of grass. It also appeared healthy and was green. Your thoughts are welcomed as to the above mentioned problems. Thanks in advance.

Answer
Brown sections: If this occurs as thin strips, they could be due to the edges of the sod pieces drying out. Fill in the seams with sand or top soil.
Clumping: Usually caused by  mowing wet turf or the grass has been allowed to grow too tall before mowing. When the clumps have dried out enough, use a blower or rake to disperse the clippings.
Uneven surface: this may be caused by not leveling the soil before laying the sod. Using a roller might help restore contact between sod and soil and level the surface.