More detail is required and a few pictures.
Is this in the open garden or in pots?
What do you mean by white paint as well ?
You will never see fly eggs,my suspicion is that is season long food ,but again pictures needed.
That is a glysophate weedkiller, so will kill the grass and the weeds, if that is the way you really want to go,it is not instant and you will not see any results for about 2 weeks.
Now as for just laying turf on top,you can,after you have prepared the soil, which means turning it over and...
I would take it out of that pot ,it is too big,for such a small plant,needs potting down .
To water 3 times a week is just too much,that is the other problem.
So pot down ,less water,when it shows signs of growth again, move on.