Q.Good Morning. I Am Prof Cecilia Kachelhoffer From South Africa
I would like to have a recipe for a homemade weed killer.

Certified GKH Gardening Expert
One good natural weed killer involves boiling water. Simply boil water and pour it directly onto weeds. The high temperature will damage the cell structure of the plants, effectively killing them. This method is best suited for areas where you want to prevent any vegetation growth, as it doesn't discriminate between weeds and desired plants, however this is my preferred method.
Here are some more tips:
https://www.gardeningknowhow.com/plant-problems/weeds/safer-alternatives-to-roundup.htm
https://www.gardeningknowhow.com/plant-problems/weeds/using-organic-herbicides.htm