Head to the right. Smash the soldier hiding under the flower and break the pot for a red potion. Jump across the gap and hit the second soldier. Continue to the right, defeating two soldiers hiding in tree stumps along the way, then use the potion on the grey blocks to enter the well.
Smash the soldier hiding under the pebble and jump left. The first platform's pebble doesn't hide a soldier. Collect the meat and jump-attack the second pebble, which does hide a soldier. Destroy the blocks with potions (the bottom-right block contains a bag of gold) then stand on the water spout to return to the surface.
Continue right, ignoring the well this time (you can go back in if you wish, but the food and gold won't reappear). Jump over the gap to face another tree stump soldier. The blocks contain a coin and a crossbones. Continue right, hitting the last tree stump soldier and collect the key from the vase. Press up to open the door.
Boss: wild boar
The wild boar races back and forth, pausing when it hits a wall. Hit it three times to turn it into a roast boar. To fight it without taking damage either use jump-attacks or else wait until it runs into a wall then hit it before it turns around and comes after you again.