If you want to sell something just tap on your trading cart, choose an empty crate, choose an item you want to sell, then choose the amount and the price. You can sell all goods from your storehouse and barn (but you can’t sell tools).
If you want to get back in stock something that was put for sale it will cost you diamonds.
Please note that only bots (fairy tale characters) can sell goods for diamonds. Players can only sell goods for coins.
"Fairy tale characters" are NPCs (Non-Player Characters) On the market, they are represented as the Wolf, Cinderella, Little Red Riding Hood (with corresponding avatars), who can sell goods not only for coins, but also for diamonds, and such characters cannot be accessed on the map.