How do I get wooden cogwheel needed to Stone Mill?
You need to have a building that produces them.
If you click on the building menu and hover over a building you see a list of items.
Under “Stellt her / Produces” you’ll find the products a building can produce.
After the building is finished, click on it and select how many you want.
Small hint: “wooden cogwheel”. So looking for a building that uses wood and produces wood products is a good start.