Q.Marsh marigold like plant
We have what looks like marsh marigolds growing in a relatively dry area of our garden and are very invasive to my lawn. What is the best way to curb them?

You may have Buttercup weeds, they have a similar flower to a Marsh Marigold.
These links will help you.
https://www.gardeningknowhow.com/plant-problems/weeds/how-to-kill-buttercup-weeds.htm
https://www.gardeningknowhow.com/plant-problems/weeds/how-to-kill-buttercup-weeds.htm
https://www.gardeningknowhow.com/ornamental/flowers/marsh-marigold/growing-marsh-marigold-plants.htm