Can moss, weeds and gr mix as compost?

Yes but be careful with the gr. It tends to clump and not decompose for years. Just a little sprinkle. Also add a sprinkle of garden soil like a starter. Water well. I put my gr clippings around the outside of the compost bin to keep the weeds back. My property is sizable for a city house and it's an easy way to kill the constantly growing weeds. If your pile is full of ants that means it needs more water. No meat products like fat or scraps. Just egg shells, coffee grounds and vegetable matter.