Q.Avocado Tree Desease
The leaves are a bit yellow with a brown circle The have fungus on the other side of the leaf And now that I took out all those leaves out and new ones arrived, there is something eating the leaves

Certified GKH Gardening Expert
Likely, whatever is eating the leaves will be the cause of the fungal infection. Without microscopy, it would be hard to call this one.
Generally, a combination of insecticides and fungicides will be necessary, here.
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm
https://www.gardeningknowhow.com/plant-problems/pests/pesticides