If you have a shortage on goods you can buy them in the goods shop. You can enter the goods shop via the trade center or by directly clicking the "goods shop" button in the menu.
- Click on the "goods shop" button in the menu to open the goods shop
- Click on the resource you want to buy and choose the building you want to store them.
- You will receive the goods instantly
TIP: The offers in the goods shop change every three hours, so check it regularly. Sometimes, you might even be able to get goods for free.