Kikuya lawn regrowth

Hi everyone, long time redditor first time poster. My lawn is dying in some parts, dead to the point of dirt in others and thriving elsewhere (see pictures). I think it’s diseased and has slowly progressed and thinned out. How can I kill this disease? Or promote regrowth.

I’ve tried re-seeding the dirt part but it didn’t work obviously. Looking for guidance and advice if it is diseased or too far gone and needs a replant.

I’m unsure how I’ve managed to kill, half kill and grow very well my lawn in a space of a few meters hahaha.

Thanks in advance!