Question
why do i get toadstools growing on my lawn.

Answer
Toadstools can come for a couple of reasons.
Too much dampness ( rain , watering the lawn to often etc) and too little sun on that area,and from decayed wood under the ground.
Toadstools are fungus, and sometimes when a tree root dies, it will rot and a fungus will grow, so it makes toadstools grow on top of the ground over the decayed wood (it can be any piece of wood under the ground, like left over from construction etc)
Soak the area with a fungicide enough to get down to the dead wood.
You might dig down and find the wood or root and remove it.
A fungicide will kill any mold or fungus.
If it is not enough sun to the area, you might want to prune out enough limbs from trees or shrubbery so that more sun can get to that area.
Charlotte